How can I make subtitle and insert it into a DVD menu

Hi, I need to know about four things:

1. Which is the best subtitle maker app to use

2. How can I create subtitle on it

3. How can I link this subtitle with my movie file
4. How can I insert the subtitle and the movie into de DVD menu as an option

PS.: I used FCPX to edit the movie and I still have the project file.

Thanks