No sound after car radio replacement

[catweazle999]

i am trying to replace the original radio with a new car radio system, i connected the power supplies and all 4 line out speakers, but no sound at all, i heard there is an external amplifier somewhere near the trunk and this amp must be switched on anyhow, i have tried to connect the remote Antenna cable without success. I have a Genesis Coupe 2013 3.8 ltr with the Infinity Sound System. Any help would be appreciated, cheers, Ray