Welcome fo the openHAB forum 
Your topic title gives your final goal, however you are not there yet. I suggest you go step by step.
You can see your MQTT devices report temperature and humidity via MQTTfx, so your problem is concerning openHAB and its connection to MQTT.
I have to assume you are using a openHAB version 2.5.xxx, hence you are using the MQTT binding version 2, however this one needs a different syntax to link items to thing channels ( which you probably haven’t created).
Most users use such devices flashed with Tasmota, so there are a lot of tutorials reflecting such, see Here