Rear AUX power Outlander max

Just purchased a wrap around rear cargo box with tail light and passenger hand warmers…..which brings me to my first question here on this site……where do i get key’d power for the heated grips, and where is the best place to tie into the tail/brake wire for the light on the box?
The connector for the box is the same as a 4 prong trailer connector.
the box is from WES industries
http://wesindustries.com/rear-cargo-…max-2013-2014/
fit and finish is nice, but zero info as to hwere the best place is for wiring

thanks in advance