Here's what I did. On Amazon, I ordered a Meanwell power supply model number RD-35A for somewhere around $23. That is a dual 12v and 5v power supply. I chopped off the end of an old monitor cable and added some crimp on connectors to provide 120v to the power supply. Using a multimeter, I determined the V1 connection was +5.2v, the common was Ground and the V2 connection was +11.9v.
Then I ran wires from the V1, V2 and Ground to the three screw connector on the same side as the USB ports of the large breakout board. Note that the right side of the terminal block is marked +5v and the left side is marked +12v. Place the common (ground) into the middle, and Voila, we have power. If I were really smart, I'd have selected a cord that has a power switch inline somewhere. As it is, everything runs from a power strip, and I use the switch on it after doing the shutdown routine on the APi.
The only reason for the dual power supply is to provide 12v to the audio amplifier that is in the APi. If you are going to be using an HDMI monitor with speakers through the HDMI connection, you can just look for a similar power supply on Amazon that provides 5 volts at 4 amps to be sure you have enough. It will probably be somewhere around $18.