Scrape away the plastic coating over two solder pads at the center of your LED strip.

Grab the jack side of the waterproof power connector and solder the red wire to the positive (+) pad on the LED strip, and the black wire to the negative (-) pad. Slide a large piece of heatshrink tubing over the LED strip and the newly formed junctions.

Add a ziptie, some epoxy, or both to provide strain relief and added waterproofing at this delicate spot.