You can either apply directly to the cruise lines via their web sites (see a list of links to cruise-line employment sites here: http://allthingscruise.com/.../ ) or you can sign up with employment agencies specializing in cruise jobs. You'll find links to these (along with other info. about what it's like to work on a cruise ship here: http://allthingscruise.com/work-on-a-cruise-ship/

As to whether you can get on the same ship as your boyfriend, I would guess that would really depend on the ship's labor needs and yours and your boyfriend's qualifications.

Good luck!