Download the Arduino software
to your computer (it's free!) and open the "DIY Computer Mouse" sketch. The "DIY Computer Mouse" sketch can be found on this page in the "Additional files" section.
Build your circuit (see the photo gallery for an image of the setup). Make sure your two dimmers are connected to the analog input pins, A1 and A0, and the button is connected to D0.
Plug the micro USB cable into both the Arduino module and a USB port on your computer.
Turn your power module on. You should see a red light illuminate on the power module and a yellow light flash on your Arduino module.
In the Arduino program, select your board. Go to Tools>Board>Arduino Leonardo. This littleBits Arduino module is modeled after the Arduino Leonardo and is therefore compatible.
Next select the serial port that the Arduino will communicate over by going back to "Tools" and selecting the correct port in the "Port" section. The name of the port will depend if you are on a Mac or Windows computer. On a Mac, it will start with /dev/tty.usbmodem... and a PC will start with COMM… In Windows, you can look for the USB serial device in the ports section of the Windows Device Manager. If you are on a Linux machine, the port will look like /dev/ttyUSB…
To upload the Arduino sketch to your Arduino module, press the arrow button in the top left corner of the screen. You will see a blue bar at the bottom of the window that says "compiling sketch", and you should see two yellow lights flash on your Arduino module when this happens. The upload is complete when you see "done uploading" at the bottom of your sketch window.
Once the program is uploaded, you will be able to control the position of the mouse on your computer screen with the dimmers and left click with the littleBits button.
Note: If you keep the dimmers central, you can regain control over your actual mouse or trackpad.