Be sure to follow the guide below to install the board and libraries. When you've successfully install the Bluefruit Arduino libraries, come back here and continue the tutorial.
To load the sketch make sure the libraries above are installed, and the Arduino is connected to the computer through a USB cable. Under the Tools -> Board menu make sure the Adafruit Feather 32u4 is selected, and under the Tools -> Port menu the serial port for the Adafruit Feather is selected.
Then press the upload button or click the Sketch -> Upload item to send the code to the Arduino. Woo-hoo the sketch should be running.
You can modify values in the code to make different keyboard characters or set GPIO pins.
On line 108, you can change which GPIO pins will connect to the Cherry MX switches.
On line 109, the array lists which keyboard characters correspond with the GPIO. The keycode.h file contains all of the available keyboard characters.
Before you can use the HID keyboard, you will need to 'pair' it to your phone or PC. The pairing process establishes a connection between the two devices, meaning that as soon as your phone or PC sees the Bluefruit LE module again it will automatically connect.
The exact procedures for pairing the keyboard will varying from one platform to another.
The Bluefruit Keyboard will appear in an available list in the Bluetooth device settings. Just select connect/pair.