Your NeoPixel strand has 3 wires. The red wire will connect to VOUT, the middle wire to A1, and the third wire to GND.
Be sure you're connecting to the correct end of the strip! Always connect to the IN end. If you connect to the other end of the strip, it won't light up.
The IN end is usually the end with the male connector, but not always - sometimes a shipment of lights will be wired up differently, so it always pays to check. If you lay out the strip as shown in the wiring diagram, with the red wire closest to you and the pixels face-up, you should have it correct.