The way I understand it, small height adjustments can be done with the spring “preload” adjuster rings, but it is not ideal for this purpose because it changes your sag setting and messes with your limits in suspension travel. The spring adjustment rings will change the ride height but not the spring stiffness. Height adjustment is best accomplished be replacing the links in the rear suspension, or getting adjustable links, or a different shock/spring (most expensive route). You still have overall limitations because you are changing the swingarm geometry or you may have the rear wheel hit the fender in the case of excess lowering.
Short answer to the question: install different links or a different spring/shock.
Here is a thread with the same question: Raising links ??