Ok I will try to help.. The wires connected from the rear speakers going to the amp have an inside wire and a shield (PER SIDE) do you have the inside to the + and the outside to the - ?(it doesn't look like it is in the pictures)
If not that is what you need to do. Turn the gains down because if they are set to high you will kill the amp or the speakers or both. So the way this should be wired is. The rca middle wire to + the outside wire to the -, from there, the rca's plug into the "input" on the amp. set the crossover to LP from there wire the subs to the speaker connections on the amp.