How do I use my W3 wireless adapter with the A2+ powered speakers, since they don't have a USB power plug built into the speakers?

Plug the W3 AC Power Supply (one adapter is included with the W3) into an AC outlet, connect the W3 Receiver into the adapter, and run the mini-jack cable from the Receiver to the A2+'s. If you're not using your W3 transmitter with a computer, and need a second power supply for your setup, you can find extra power supplies here. You can also use spare USB phone or tablet chargers to power the W3, just make sure they can supply at least 500mA.