String heat shrink tubing on the wire of the voltage regulator using heat shrink that is 1/4" to 1/8".

Bring the voltage regulator wires to the solar panel wires and prepare to solder.

Make sure you solder red to red and black to black.

Make sure to solder on top of a scrap piece of wood or other material. Do not solder over the open box in case solder drips down into the box.

For instructions on how to solder please visit: Soldering Skills