This is the best I can do for now as I am travelling, in terms of getting photos of the cables to the card:
The yellow cable with the 3 black ends is a multi-power cable for up to 3 HDX cards.
This came with my HDX card from AVID and has a 6 pin female connector.
I also have another cable for PC's with that card but I am not using that for this computer.
The Belkin cable kit has a 6 pin to 6 pin cable, as well as a bunch of other cables which are also unused.
All you have to do is plug the Belkin cable into the Avid cable, the other end of the Belkin cable to the logic board.
Then connect one of the 3 card connectors to the HDX card.
That's it.