I've discussed this in several other posts you can find here. But basically…
I've always had a fascination with / attraction to all aspects of diapers; as a kid I'd longingly envy younger kids who wore them and discovered that I loved the smell of wet diapers / peed-in clothes (mine or ones from girls, I was never attracted to the scents of other males). When I went through puberty and discovered masturbation this was part of it, also this is when I discovered that I loved the smell of girls' panties (which usually was a mixture of female scents and pee).
Over the next 7-8 years this turned into a major cloth diaper fetish and began to be a problem of sorts--I loved my diapers and I also loved girls, but the two seemed to be mutually exclusive. So, for about 13-14 years it was the “binge and purge” thing. I'd have a relationship with a girl, we'd have a fight or break up and then I'd be back to my diapers, then we'd make up or I'd find a new girl and try to swear off of my diapers…over and over again.
So I realized fairly early on that any relationship with a girl would also have to include my diapers. But the idea of letting girls in on the secret scared me to death. So I learned to drop hints and look for signs. A good time to do this was if / when the topic of someday having kids came up. I'd make some remark about “changing all of the wet stinky diapers” and if the girl reacted negatively ("Oh I don't want kids because I can't stand the idea of diapers!") that made it pretty clear that she'd also never tolerate mine. This happened most of the time.
But once or twice I'd find girls who didn't seem to mind, “Oh I wouldn't mind that, I babysit a lot and change diapers and it doesn't bother me at all” etc. So in these cases as opportunities arose I'd continue to find out more.
And usually, my introducing the idea that I wanted to wear the diapers coincided with us becoming intimate. That's a good time to discuss fantasies and after asking about hers, she'd ask about mine and I'd usually say “I want to be treated like a baby" then--depending on how that went--eventually, the rest of it.
This (as documented elsewhere) had varying results. But, bottom line, pretty early on I knew that I loved my diapers and could never have a long term relationship or marriage without the girl knowing about, approving and (hopefully) being part of it. I knew I could not hide it. At some point, as the relationship became more serious and the usual discussions (politics, religion, etc.) were had, one of them had to be about my diapers!
And it was scary but also liberating. I always knew that I had everything to gain and little to lose--yes, if I did this and the relationship didn't work out I'd lose the girl but I'd still have my diapers and eventually another chance to try it again.
It's kind of like that old story about W.C. Fields, who once said “Every time I see a beautiful woman I ask her if she'd like to go to bed with me. 9 out of 10 times I get slapped, but the other one time? Boy do I have a wonderful night!”
So, the thing to do is slowly “test the water”, if that yields positive results then eventually you have to bring it up. It's part of you, they need to know it and understand it and accept it--or not. But you have to find out, and not doing so isn't fair to your spouse / partner and it isn't fair to you, either.