How to hookup trailer brakes?

Look at>Link

It>Link gives a good description of proper trailer wiring; there is actually a code for this type wiring.

Also look at:
http://www.rverscorner.com/wiring/general.html

You need to know for fact on this with a physical inspection because if you wire it wrong, you'll create a dead short for other circuits. You can't check it with a light or meter because you will read through the coil itself giving a false reading.

Once you figure out where everything goes, write yourself a note and keep it for future use because you know it's likely to happen again just about the time you forget what was what and it'll save you from the trouble a second time around.

Good Luck!