There should be a sticker that shows the belt routing either on the rad support or on the shock tower.
The tensioner bolt is a 15mm bolt and is labelled #3 pulley on the picture below. It's the one underneath the just forward and below the alternator pulley, you'll need to use the box end of a wrench most likely since you can't get a ratchet on there, the longer the wrench the better. You will need to push it towards the firewall to relieve the tension in it to get the belt on.
Either way, here is the belt routing. If you don't have a supercharger, ignore the outside belt and pulleys 1,8,9 and the #3 pulley at the front of the motor on the picture below. The serpentine belt routing will still be the same regardless.
Here is a trick using 2 wrenches, you can use it to get more leverage on the tensioner. Just be careful not to slip and hurt yourself.