Try something like: hey, can we set aside some time to talk about weird sex stuff? I have some things I think are pretty hot, and I want to tell you about them, and we don't have to do them right away or even at all, but I'd like to at least tell you about them, so I don't feel like I have to think about them in secret or anything. And you can ask me all the questions you want so it doesn't seem too weird.

Whatever you do, you want to make sure they have plenty of opportunity to ask you questions about it, because if they say "I want to learn about this - better google some porn about it" then they're gonna focus on all the worst stuff they find, rather than on the things you happen to like. It's really clutch that you talk about the weird stuff you like, rather than the weird stuff someone would find and fixate on if they look on pornhub. After you talk, give them time to think and feel and talk to their best friend about it too, because you've been thinking about this for a lot longer than they have, and they will need time to digest.

You might also want to think about how much you want or need the kink. Because you're either going to tell them:

1. ⁠I am into this kink and if you can't be down with this at-least-sometimes, there is no point in us having a relationship because I will not have a satisfying-enough sex life. OR
2. ⁠I like you, and I am really into you, and I care about your personal happiness and comfort; also I have this kink and I think it would be really hot if you were into some parts of it, and we can talk about that more now or more later, but I wanted to put the general idea on the table, while also making sure that you know I care about you.