Hi i search and with no avail came up empty handed.

i was wondering i have the music and a 04, am i so pose to plus the wire into the back of the stock head unit. Or am i so pose to plug it eleswhere. for some reason when i did my research i came across something about the XM radio. My car does not have the FM radio feature, however i did read about it being somewhere behind my driver seat, is this correct?

any help will be great TY in advance