In the setup screen, under info, you can set the fuel you want to start a session with, and how much fuel to put in at the pitstops.
Edit: Don't worry about making new threads, as long as you don't repeat a thread that is already there. Same goes for everyone. One day all the topics will have been asked and beginners can just look at the relevent thread, but we're not there yet. No point being TOO aggressive to newbies in the beginners forum, as it's there for beginners to ask 'seasoned' players how to do stuff.