First of all you'll want around this much tape and cut it.
Then you'll want to fold it around the cable with the left side facing you (depending on whether you can get to the left side or the right side of the cable, for me it was a USB cable so it was the left side).
Then fold it and cut off the excess tape.
Last of all label that cable! *cheesy rhymes inc. You can always label both sides if you wish that way if you can get to either side of your device it won't confuse you too much :)