Hi, Me (M18) and my girlfriend (F19) have been together for about three weeks now. We're both virgins, and this is my first relationship. I'm not quite sure how to initiate sex, and where to touch her in general

Last weekend, she slept over and while we were spooning she pressed her butt against my boner a few times, I responded with pressing against her and holding her tight, but it didn't lead to anything.

I'm sleeping over at hers next weekend, how can I make a move and initiate? Would be great to get some tips on hand placement, etc.