Quadtechint.com

After you learn a new ability or spell, it’s time to add it to your action bar.
This allows you to use it easily in battle. Click on the Abilities button on the
bottom of your screen. This button looks like a book. You can also press the
“I” hotkey.
In your Abilities window, you see your attack ability, along with any other
abilities you already have. An ability that has the “passive” tag next to it does
not need to be activated and is always on. These types of abilities never
need to be placed on your action bar.
The ability you just learned should be on this ability page. If you learned a
spell, it will be on the spell page. In some cases, you might have to click on
the spell or ability tab at the bottom of your book to access it. Mouse over the
new spell or ability icon in your spellbook or abilities book to see what it does.
Then add it to your action bar. Left-click and hold the icon. Then drag it onto
the third slot in your action bar. It now appears there. You can now use it by
clicking on it or by pressing the appropriate hotkey, which is the 3 key.