At the tensioner pulley, there will either be a bolt or more likely a square hole to place ratchet in. Rotate it counterclockwise. The bolt you are loosening is most likely the bolt that holds tensioner to engine.
I believe it is an 1/2" ratchet. You may have to use a breaker bar to get leverage if the tensioner has good tension on it.
Here is a close up of tensioner: