I'd recommend that if you're not "wired" to be a bottom (as so many gay and straight men are), that you buy a set of butt plugs (they come in three sizes) and experiment with having something inside you while you masturbate. The initial "surprise" to an uninitiated sphincter muscle can be rather painful. So, getting familiar with what does and does not feel good as you learn to enjoy your anus as an erotic zone is rather important.
Then, when you meet the right "top" or understanding friend, go slow, use lots of lube, always use a condom, and don't give up if it doesn't exactly ring your bells the first few times you try it.
My ass is more or less retired these days, reserved only for The Squeeze to enjoy when he's in the mood. More often, he's in the mood to have me enter him and then, when he's worked himself into a major hot state of mind, I slowly -- and affectionately -- fuck him. That's about the only way he can maintain a serious hard on, rather than me just pounding the hell out of him. Actually, it's the affection I lavish on him that pushes him over the edge.
Don't worry about admitting to prospective partners that you've never been fucked. We've all been there. And, if it isn't something that you find sexually stimulating, don't lose any sleep over it. A lot of men (and women) just can't wrap their libidos around the idea of anal sex. But when you engage in it with the right person, a man who knows what he is doing, it's very easy to lose control and have an incredible, mind-numbing orgasm that can last more than than normal.
Good luck. Be safe. And definitely practice with various sizes of butt plugs or dildoes as training wheels before riding hands free for the first time.
When he fucks me, fortunately he's just the right size (some where between 7 to 8 inches, depending upon how turned on he is), and with him I find the experience of having my ass filled with his wide, uncircumcised erection to be pleasant enough. But there's a lot of trust shared between us.