If you already have a friend lined up. You should practice with a butt plug or dildo or the like. Get used to using lubrication preferably a product intended for that purpose. Get used to being penetrated and see if you even like it. When you get with your partner ask him to loosen you up with lube and a finger. He should be wearing a condom if you aren’t both protected. Then ask him to enter super slow and you have to relax and let him know to go slow until he’s in. Try on all fours first. Then communicate and let him fuck you as long as he likes and let him know how great a job he’s doing at fucking you and how badly you needed it. Let him know you’re a virgin he will be very enthusiastic. Try not to come until he’s fucked you a few times so you don’t lose the mood.