First, you download an "UnoJoy", than you put code in Arduino (in the folder of UnoJoy, called UnoJoyArduinoSample).
Than put arduino uno r3 in "DF mode" (you make this by touching 2 pins on the 6 pin connector, closer to USB B connector, (where you put an USB cable)), than start "TurnIntoAJoystick".
Than, you connect your buttons to pins 2-13 and analog pins (in the folder, there are written coresponding buttons to pins, or try it with metod - try and error, like me :D
When you want it to be not as joystick, but normal Arduino, start "TurnIntoAnArduino".
!!!!!!!!!! The buttons must be connected to ground on Arduino, not 3.3 or 5V.
And that's pretty much it :P I hope this helps :P