I would not recommend using scissors, they don't work very well for cutting nor stripping. You might want to find someone locally with electromechanical assembly experience. The kit is targeted at the sort of folks that have cut/stripped wires and read wring diagrams before.

Also there aren't any official videos on mechanical assembly, so depending on what video you watched it may not have been correct or applicable to the version of kit you have. The PDF instructions stickied on this forum are the official instructions.

2.) Cut the 12v cable coming out of the power supply approximately 12 inches away from the power
supply. The 12v cable is the one that does not plug into the wall.

The instructions say to cut the 12v cable to approximately 12 inches. This is because you don't need all the excess cable. Do you have a pair of wire cutters? Scissors aren't made to cut wire, but they'll work if that's all you have. I would strongly suggest a pair of wire cutters/strippers, though. You'll be doing a fair bit of wire cutting/stripping and it helps to have the right tool. They are usually $10 or less from your local hardware store.

Be sure to follow the instructions verbatim. If you do so, everything will come together perfectly in the end.

If you need additional help, don't hesitate to ask.