Slide the neopixels a little way out of their silicone sleeve. Find the "in" end of the strip (arrows pointing away from you) and tin the three solder pads with your soldering iron.
Cut three 6" pieces of stranded wire. Strip a teeny bit off one end and tin the exposed wire. Solder red to the + pad, black to G, and white to the DIN pad.
Solder the other ends of the wires to the Circuit Playground: red to VBAT, white to pin 6, and black to GND.
Plug your battery in to your Circuit Playground and be sure all the lights come on. Press the button and see the modes change.
If the lights don't come on on both the Circuit Playground and the LED strip, here are some things to try:
- Re-upload the code to your Circuit Playground
- Check to be sure you soldered to the "in" end of the pixel strip -- it won't work if you solder to the "out" end
- Be sure you're soldered to pin 6 on the Circuit Playground
- Make sure there are no shorts; i.e. your wires or solder joints aren't touching each other where they shouldn't be
Once you've got everything working, it's time to seal off the neopixel strips to keep them nice and safe from sweat or bumps in the night.
Cut a small piece of 1/2" clear heat shrink and slide it over your solder joint. Squirt some hot glue inside, then quickly grab your heat gun and shrink down the heat shrink while the glue is still wet. This will create a solid plastic seal around your connection and keep it safe from just about everything.