Just replaced my daughter's tensioner today. The mechanic that replaced her belt before damaged the tensioner and bent the adjusting rod because he did not know how to reinstall it properly. You must first loosen the large bolt that goes through the center of the tensioner first (this locks the tensioner in place once adjusted). Then you can loosen or tighten the tensioner pulley using the brass colored adjustment rod that sticks up vertically (actually a little to the right when facing the car). Her adjustment rod was bent and stripped from someone trying to adjust belt tension without loosening the large center bolt first and the tensioner was blown out and had no spring resistance when I removed it.
Put new one in and it works like a champ now. Had to remove fan pulley (to remove tensioner bracket), power steering pully (to access other bolts on bracket), and water pump pulley (to install new tensioner). Also had to disconnect shock from tensioner at tensioner bottom which is shown in one of the the pictures above.