How do I switch on the backlight on the WASD Code Keyboard?

The user's guide for the WASD v2 keyboards (including the CODE) can be found here.

You will note that Fn + F11 and Fn + F12 are used to adjust the backlight, but will only function if DIP switch #6 is set to the ON position on the bottom of your keyboard.

^{Source: This answer was typed on a CODE keyboard. :-)}

Function + F12 toggles backlighting on/off. Function + F11 should cycle between the backlighting levels, from lowest to brightest.