Unless it's got a means of turning itself on, you'll either need to connect the 24-pin so you can jumper 14 (usually green) to ground to kick it on, or find which pins are those on the PSUs' 24-pin socket and jumper there.
Yep. I put the jumper directly on the PSU to avoid having that thick ass wire around for nothing. Easy to do if your wires are coloured. Just look for which pin connects to the green wire, and short it to any pin that connects to a black wire.