To enable these cheats, press B to show the options, then you can do the following to activate the corresponding effect. Press B to exit.
Change health level: press L or R, then press Black, White, Black(3), then hold A and set a new health level.
Change magicka level: press L or R, then press Black, White(2), Black, White, hold A to set a new magicka level.
Change fatigue level: press L or R, then press Black(2), White(2), Black, hold A to set a new fatigue level.