The kit includes two pre-crimped 8-pin headers with a rainbow of wires coming out. Separate, cut, and strip the wires as shown, and solder them to the tip pin of each jack.

Note: On the photo, I’m using 1/4” and 1/8” jacks, and you will notice that each 1/4” jack has a corresponding 1/8” jack directly soldered to it. Your kit might include banana jacks, or some other type of 1/8” jack. The particular type of 1/8” jack used in the photo didn’t ground itself to the box: therefore I had to run a ground wire between the jacks, which I connected to the last 1/4” jack.

Same thing from a different angle:

10) Now plug in the other 8-pin connector on the X header and separate the wires down the middle into two bunches of 4 wires...

... and solder 4 of those wires to the jacks on the red side of the matrix:

... and solder the other 4 wires to the jacks on the green of the matrix.