Everyone talks as though penis-in-vagina sex was the most natural thing in the world.  Eh.  Sure.  For humans walking, throwing a rock, and talking are all totally “natural” but we don’t do any of those things perfectly the first time either.

That’s not a problem, by the way.  It’s a lot of fun learning.  Unless you think you’ve failed if it doesn’t go perfectly first time every time.

Take your time.  Work together.  Don’t leave (unintended) bruises.  Don’t blame yourself or your partner.  But also don’t give up.