I was raised catholic, and the steps you need to complete, the sacraments, would be baptism, which I would think is a freebee as they do it to babies, first communion which we did around 1st grade. I went once a week to a school in the evening until the third sacrament, confirmation, which is your “I’m an adult and chose to be a Catholic” . That was around 15 or so, similar to a bar mitzvah.

There are a total of seven sacraments, last rites at death and a Catholic wedding are two others I believe.

There really weren’t tests and such, I could name a few more saints than the average person I suppose.

I’m sure a local church will have adult classes, I can’t imagine it being a difficult process, though how long it would take I have no idea.