basically you will need a good length of wire and large ring terminals.
cut the wire to length and crimp the terminals on. you may also want to seal the connection with heatshrink tubing instead of those cheap covers that come with most terminals.
you will also need to decide how you will connect all the wires. you may want to get a nice negative battery terminal with a bunch of connections. or get a good distribution block to run all the 8 gauge to and then from that run 4 gauge to the negative on the battery.