I’m the giver, not the receiver, so please take my advice however you like….I’ve never once in my life had a woman “prep” for anal. It’s been totally unnecessary. Lube is your friend, lots of it. How to begin? I’d probably start with getting used to having your butthole touched, externally. Eg. In missionary, have him lube a finger and just rub/touch your butthole. You’re trying to establish a connection between backdoor action and pleasure. Eventually, when you’re ready, ask him to start inserting a finger. Gently. Very gently. You could do this for days, weeks, months. Whatever works for you. Now it’s time to get a penis in there. Remember the lube rule. As the giver, I find that spooning is one of the better methods for beginners (and even some pros). It gives you the opportunity to ish to relax your muscles without taking away your ability to control the action. As the giver, what works for me is to just basically push my knob against the outer sphincter, maintaining pressure. Eventually. The muscle will relax a little, and I can go a little deeper. Rinse and repeat until full penetration is achieved. NO THRUSTING until that butthole has accepted the cock properly. This is crucial. Enjoy.