The basic concepts have not changed:
- configure/discover things
- link the channels of the things to items
- setup your UI for your items for interaction
- (automate via rules)
… then you just scratched the surface there. 
PaperUI was intended for administration and not as interface for “end users”…
And: PaperUI has been abandoned with openHAB3.
Therefore you really should read about the new MainUI when continue trying to get into openHAB3
Probably start here: Building Pages in the OH3 UI: documentation draft (1/3)
Some hint though:
Simple example regarding your setpoint-question (out the many options now) is to add a “cell” or a “card” to one of your “pages” and connect your setpoint item to it, e.g.
… results in that interactive card:
