Hi there, Kaz and welcome to the boards!
There is nothing to be sorry for, we are glad to have you here and that you felt safe sharing that with us.
You are by far not the same person with similar worries, a quick search of the boards or our main site will show you that, if you want to read through other people’s experiences.
You know, I’m not at all surprised you don’t know what to do or how to have sex with your partner. How could you if you two haven’t had it yet or talked about it, which it sounds like you have not? There is no given set of instructions or rules about any kind of sex with any kind of partner, no matter the chromosomes or genitals they have, period. Thinking there is one, would be like thinking everyone’s favorite food is pizza and automatically ordering a salami pizza for you and your friend who is staying over, instead of asking them what would they like and thinking about what you would like yourself first. Does that make sense?
Heather talked more about all this in this old but still accurate advice column with a question very similar to yours:
How do lesbians have sex?
As for your situation, have you two already talked about if sex is even something both of you want and how you might potentially want it? If not, how would you feel bringing this up with her and do you want any help with that? We can definitely help you brainstorm how to start that conversation if you are not sure.
We also like to give our users this amazing article about communication about sex:
Be a Blabbermouth! The Whys, Whats and Hows of Talking About Sex With a Partner which I think might be helpful for you too.