How do I hook my MP3 player up??

[Camaro_94]

I have the bose stereo system in my Trailblazer and am wondering what I need to do to hook an MP3 player up to it. I used to have a cassette tape that I could put into the tape player in my Formula and run an MP3 player through that, but I was wondering if there was a connection in the back I could plug into in the Trailblazer, and if so, what I would need.

Thanks