First date or fifth? When do you actually mention it?

Back on the apps after a long relationship ended and I have hit a question I never had to think about last time round, because that one started when we were both very young and everything came out gradually.

Now I am meeting people as an adult with a fairly clear idea of what I like, and I do not know when this is supposed to come up. Too early and it is the only thing she knows about me. Too late and it feels like I have been sitting on something.

For those of you dating now, when do you say it? And does anyone put it anywhere on a profile, or is that asking for trouble?