I've never found it easy to talk to anyone about why I enjoy watching women fight and wrestle. My wife knows, but she found out about it accidentally. She tolerates my "fantasies," but she's never participated.
In hindsight, I wish I had been up front with her from the beginning, though. I think it would have been easier than the way she found out, and I wouldn't have felt the need to "sneak" around about the subject.
Your situation is much like mine. Wife knows it and tolerates it. However, I think that at this point, she gets it. I did a fairly thorough job of explaining it when she finally found out. Thanks to websites like this and Barb's, I was able to come to some logical conclusions as to "why" and when I laid it all out, it made sense. As far as being up front in the first place, that just wasn't possible. We were so young. I knew it then, and she agreed that she wouldn't have been nearly as receptive as she was after decades of marriage. Lastly, I posed the question: "When we were younger, if I were wrestling against some other guy, with my shirt off, would it have turned you on?" She had to admit that it probably would have. That was the last it was ever mentioned.
In regard to starting a conversation with your love-interest, I'd say that there just isn't an easy way to open the subject. You have to gauge that for yourself. I tried to lay out bait on several occasions, but it was never taken. And, it's OK to have some secrets, provided that they're not dangerous. Eventually, they're going to be discovered. My advice is to be ready with a reasonable explanation when that happens. Heck, I still try to hide the fact that I purchase an occasional video. Old habits die hard!