Have that conversation!
Just what the title says. I see, and have experienced it, a lot of people asking "How do I bring this up?" Just do it. The 6th i finally got brave enough to do it myself. Told my wife that I had been wearing one for the last 3 days, she was sick so no fun time, and I really liked it and wanted her to hold my keys. She was a little apprehensive, and angry that I hid it at first, but we had a good conversation. My wife is extremely vanilla, in every way. Lingerie and toys is where she really stops, and that was fine! But I wanted something. I always loved the thought of chastity and loved it when I wore them in the past, but having to lock and unlock every day was tiring. She thought it would hurt and I made sure she understand that it didnt, was comfortable, caused me no harm and that I loved it.
My wife has come around a little, shes still a little apprehensive, but she has definitely loved the changes in me so far. (Calmer, more attentive, more affectionate) She is kind of coming around slowly. She will playfully grab it every now and then to tease, she loves that I am making a bigger effort in all sorts of ways. So it worked out. I am so much happier now. She even picked out a chastity belt to help it stay snug. A pink one that says "Owned" on it. Instantly hard when she did that.
Just remember there is a chance this wont be your experience, your partner may flat out say now. Just dont get angry with them if they do. This isnt for everyone. Some want no part in it. I thought mine would be that way but she surprised me. I did tell her I planned on continuing to wear if she said she wanted nothing to do with it and that if unlock when she wanted play.
Take that leap and just be honest! You may be surprised too!