Moving to the front, theleft earcup has a clickbutton that allows you to switch from the optical input or the stereo input on the base, while the right cup controls the four EQ options that are available.
And if you need the how-to instructions, click on the building guide mode - top left, third button - and it will give you the option to watch the item being built or alternatively you can generate a step-by-step building guide which you can then print out.