On my '12, there are oval plastic knock outs at the front of the bed. I had to drill holes in them for drains from my roll up bed cover. No reason you couldn't use them as a similar passage into the bed for wiring. Run positive from the battery back using heavy wire. Technically you could connect the negative to the frame back by the bed, but personally I would run a return wire up near where the battery is connected to the frame or engine, perhaps even the same bolt.

It is my understanding that with the battery charge monitor, you don't want to connect both the positive and negative wires directly to the battery.

--Rick