Each drive belt has it's own tensioner of some sort. I don't remember exactly how they all work but you have to remove the fan from the pulley and then you can slip in/off all of the belts. It's been a while since I've done mine so hopefully someone who has done this more recently will be able to chime in with where they are located...
.. For future reference, your thread title sucks. It doesn't draw anyone who might know the answer to the thread because no one has any idea what your looking for without clickin on it. I honestly thought it was gonna be a picture thread. Your title should be something like "changing drive belts?" and then someone who has changed their drive belts recently might click on that and help. Furthermore, someone who is using the search feature in months down the road to search for a thread on how to change drive belts probably wouldn't find this thread, even if it ends up containing a nice, helpful answer.