Talk to your guy and ask him for permission as you’re going in. That’s the kind of behaviour that can put a guy off from getting f**ked for a long time, so, be incredibly gentle at first and work slowly together. It can really hurt when a top just sticks his cock in.
Don’t just shove your cock in as if he’s a fleshlight (unless that’s what he likes and you’ve already talked about it). When a bottom guy gives you his ass, he’s assuming you’re going to look after it. Being a top comes with a lot of responsibility