if you go through my archives, you’ll find The Vice guide to eating pussy. it’s really the best explanation of how to do it!
and just be natural. don’t try to be “cool” or whatever. just go with the flow of whatever she’s doing. it’ll be fine!
the great part of lesbian sex is that you are basically doing what you do to yourself to someone else. and ask her what she likes! some girls don’t like fingering or they do but a certain way. communication is the best!