How do I put it in?

I'm male(19) and never had sex neither has my gf(18) and we were trying last night for the first time but were finding it difficult to put it in.

Is it supposed to go in very smoothly?

She was very wet and said she felt ready, and she said it started to hurt so I don't know if I was able to put the tip of my penis l in a little or it just hit her vagina.

So need help as to what I can do to you know put it in. Like I've never put it in so am I missing the hole or what can be done to make it better next time. all suggestions welcome.

Advice?

TL;DR: first time and couldn’t get it in. Advice?