Mac Forums

So i got a new imac...kinda it was my sis but i have it now and i restored it but with itunes how do i transfer the music from my phone onto the computer? cause when i try to do it when i hit sync it says it will earse all my music and put the music from the imac on it...which is not...so how do i transfer the music? and like...i have music i didnt purchase like it was free i got it from datpiff...indie so yea not illegal i dont do that **** I AM RUNNING MAC NOT WINDOWS! and no programs just using itunes how can i do this?