Adafruit BlueFruit App
Go to the app store and find and install the Adafruit BlueFruit app on your smart phone.
Launch the app. Make sure you're in "Central Mode" and that your Feather is powered up. You should see the CIRCUITPY drive appear on the main screen. If it's not there, try pulling down to refresh or restarting the app.
If you still don't see it, try re-uploading your code, making sure you have all the libraries installed. It won't work without all the libraries! Circuit Python still lets you save the file without throwing an error, so double check you've got everything you need.
Click Connect, then Controller > Color Picker. Choose a color and press the "Send selected color" button. Your lanyard will update with the new color. Like magic!
Now go back to the Control Pad. You'll see four buttons and four arrows. The number buttons will select between the four color palettes you made, and the up and down arrows will speed up or slow down the animation of the gradient.
Slide a piece of clear 3/8" heat shrink over your solder connections. Squirt a little hot glue inside and then shrink it down with a heat gun while the glue is still wet. This will make a rock-solid, unbreakable plastic casing for your delicate solder connections.
Slide the lights inside the webbing so they're centered, with an inch or two at either end for overlap. You can finish the cut edges of nylon webbing with a soldering iron (use a tip you don't care about) or a lighter.
Fold the lanyard ends over one another and sew or glue them down to make a secure loop. Attach your lanyard swivel hook to the point at the very bottom.
You can either tuck the Feather and battery into the back of your badge, or use the mounting holes to sew it to the back of the lanyard. A 1" lanyard will cover the board and battery completely so it doesn't show from the other side.
You can turn the LEDs "off" with the app by sending the color black. However, this will still drain your battery since the Feather is constantly checking for updates. The best way to turn it off completely is to unplug the battery JST connector.
The Feather has onboard battery charging, so to charge your battery back up, just plug in a USB cable while the battery is plugged into the JST connector.