First find the tomes in "fyrelight cave: deep canyon" area, you should find it on your way from skingrad to kvatch. To use him summon him then use the dremora training on him that should upgrade his stats a bit so he's a good partner. If for some reason you need to unsummon him, you can do that. If you have any questions post a comment. there is a glitch in the tome coding where you must drop them, but can not pick them back up if this really bothers someone leave a post and i will change it.