You probably don't have the ability to use a spell to bring them back so early in the game, so i suggest you bring a few scrolls with you when you go into a dungeon. You can buy them at Unorna's Shop in Golden lane.
Use the scroll on the portrait of your companion and it should revive him/her. I can't remember the keys but you have to target the portrait when you use the scroll rather than just use it in the area where they died.
As far as I remember - you pick the scroll with a single leftclick from your inventory, and rightclick (while "holding" scroll) on your companion's portrait.
Now he's alive ))
The discipline "Awaken" is in the "Common" disciplines page.