First wait until you're ready, then and only then do you do it. Secondly. Use lube. Lots of it. I just barley started using it and it's made it a whole lot easier. Next. Relax. Get in the mood. How? Eat. I can vouch for the majority of those. It helps if you eat them while you take a bath together. After that have him finger your butt to loosen you up. Start with his pinky and then switch to another. If you're still too tight then have him add another finger. Go slowly. It helps if you lead his penius in. You have to relax in order for it not to be painful and to enjoy yourself.

When I first did it it was not the best but after a while with the right lube and if he is gentle and cares if he hurts you or not it will feel really really really good. But don't let him pressure you. Make sure you want to do it and your relaxed other wise it will really hurt if your tense.