Spells that you cast (like swpain or shadowform) can be added to the action bar by dragging them from your open spell book down to the bar.
Some talents, like spirit tap, auto-activate.
Depending on the options you pick, to move a spell from one place to another on the bar, you may need to shift-click and drag.
Edited, Aug 29th 2007 6:29am by dadanox