You didn't specify whether the DVD drive was a slim/laptop or normal 5-1/4 drive. The slim/laptop drive will require +5VDC and the 5-1/4 drive will require +5VDC & +12VDC.
The easiest way to obtain these voltages is from a power line coming off your power supply (that connects to your hard drive or optical drive). The Molex connector is a 4-pin connector with a yellow, red, and two black wires. The yellow wire is +12VDC and the red is +5VDC. The black wires are grounds or commons. Simply splice into the perferred wire or better yet, go to RadioShack and get a male Molex connector and use that to make your connection.
I too am curious about the vertical mounting of the slot load drive. I'm doing some research now to see if I can find anything useful.