How to group items (lights)

I’ve just installed openhab2 and I’m slowly learning my way around the various configuration files. Can anyone point me to an example showing how to group items, i.e. group all my light switches/dimmers so I can operate them simultaneously.

I have defined the following in a file ‘items/group.items’:

// Overarching group                                                                                                                                                                                                                                                                                                                                                                              
Group House                                                                                                                                                                                                                                                                                                                                                                                       
// Location perspective                                                                                                                                                                                                                                                                                                                                                                           
Group basement      (House)                                                                                                                                                                                                                                                                                                                                                                       
Group main_floor     (House)                                                                                                                                                                                                                                                                                                                                                                      
Group kitchen         (MainFloor)                                                                                                                                                                                                                                                                                                                                                                 
Group living_room      (MainFloor)                                                                                                                                                                                                                                                                                                                                                                
Group family_room      (MainFloor)                                                                                                                                                                                                                                                                                                                                                                
Group upper_floor    (House)                                                                                                                                                                                                                                                                                                                                                                      
Group kid1_bedroom      (UpperFloor)                                                                                                                                                                                                                                                                                                                                                               
Group kid2_bedroom     (UpperFloor)                                                                                                                                                                                                                                                                                                                                                               
Group guest_bedroom    (UpperFloor)                                                                                                                                                                                                                                                                                                                                                               
Group master_bedroom   (UpperFloor)                                                                                                                                                                                                                                                                                                                                                               
// Lighting by location                                                                                                                                                                                                                                                                                                                                                                           
Dimmer all_Lights "All Lights" (House)                                                                                                                                                                                                                                                                                                                                                            
Dimmer main_floor_lights "Main Floor Lights" (MainFloor)                                                                                                                                                                                                                                                                                                                                          
Dimmer upper_floor_lights "Upper Floor Lights" (UpperFloor)

I have a series of UPB lights defined as items:

However, I don’t understand how I associate individual items with a group, i.e. how do I create a virtual dimmer switch that can turn all my lights on/off?

Group:Dimmer AllDimmers
Dimmer Dimmer1 (AllDimmers)


Slider item=AllDimmerd

Thanks. I think I’ve sorted it now!