Ford C-Max

OK, so we bought a 2014 Ford C-Max SE Hybrid, the ford dealer we bought from referred us to a local mechanic who does a lot of their after market stuff. They did our base plate and wiring, however we did not know where to hook the charge wire up to. I see the metal tab on the right side of the engine with the obvious (+) sign. how does one "hook up a charge line" to that tab? What type of either diodes or fuses do you need to include in the charge wire to ensure the toad battery does not discharge back into the MH??. I will not go to the local RV repair shop (long story). Another post mentioned opening the fuse box adjacent to the (+) tab and hooking up to a contact point there? We've towed the C-Max twice already with no problems, however both times it was less than a 3 hour trip. Thanks for the advice.