Use the arrows keys to move up or down and select the input to be replaced pressing enter.
Once done, choose the input you want to use for that movement. You can use Keyboard Keys, Gamepad (Buttons, D-Pad and Analog Sticks), Joystick (Stick and Buttons) and Mouse (Buttons, Wheel and moving the mouse up, down, left or right).
Once you have assigned all 4 input press F1 to test the input with the 8 directions behavior.
Press F2 to test it with the platform behavior.
Press F3 to test it with the car behavior.
From one of the 3 test area, press F4 to go back to the first layout and assign new keys.