You have to click on the control (with the mouse) in order to register a button for it. It will come up with a black box saying "Press key or controller (ESC to skip)"
It must be able to see your buttons, otherwise you wouldn't know the presets had the wrong buttons assigned.
If you need to reassign Steer Left and Steer Right, make sure you turn the wheel until it registers - a small turn won't be enough.