How to connect rca cables from stock hu to amp in 01 gmc yukon?

i want to connect an amp but dont know how does the stock head unit have any rca outputs? the amp is a 750.1 zx kicker and its going to power 2 cvt kickers subs thanks i dont want to buy a new aftermarket radio its a 01 gmc yukon slt no bose and with onstar and the hu as a cd player and a little lower theirs a cassett player like under the climate controls thanks