What stuff do I need to do? I already have  a modded Xbox360, can somebody explain the steps?

I dont have a xbox so i personally have no clue.  But did you check the tutorial?

 

http://customsforge.com/topic/901-how-to-use-custom-dlcs-in-rs2014/

 

 

 

edit:   also. you can convert the pc files to xbox easy with the toolkit.

So do I download the Custom Forge songs into a U.S.B and transfer it the xbox360. Thanks for your reply.