Depending on the type of amp you are using, you might have high-level inputs. Basically high-level inputs take signal from existing speaker wires without using the LOC or RCAs. If you are using a 2 channel you'll more than likely have a high-level input...but a monoblock amp is more than likely not going to have it.
A typical LOC has 4 wires coming from it... grey, grey/black, white, white/black... So basically you tap onto 2 speakers positive/negative wires. Then on the other side of the LOC is RCA jacks... Then connect the RCA to the LOC and run the RCA to the amp. With high-level you still tap onto the speaker wires but you run wires from where you tapped to the high-level input of the amp, and there should be a switch on the amp that says something like "input type" and you'll need to make sure it is high-level vs. low level.