Hi !
Please feel free to visit our Discord, I am always there among a lot of people and we are discussing and solving things together ! It's a lot of fun :)
In terms of earth connectivity once you get the transmitter do sth like:
transmitter.connect("earth")
and now this transmitter is connected to earth. Next is to send the thermometer value like:
transmitter.transmit("current_temperature", temp)
The INFO tab of uplink.py tells you all the info on how to connect to earth and DOCS(top right button) have even more details about how things work :)