The tensioner is on the lower left side of the motor when you are facing it. Push down on the tensioner with your hand until it is all the way down then slip the belt off. Follow the diagram in your owners manual for reinstalling it.
Find the tensioner. Sometimes they're screw-type, sometimes they're built into the alternator mount, sometimes they're a spring-loaded idler. Release it, remove the old belt, install the new one, re-tighten.
When you do it make sure you loosen the bolt on top of the motor and the one on the bottom before you try and remove the old one. When you put the new one on you will need to do it exactly like the old one was and do not forget when you put it on tighten the bolts.
350 what? for most serpentine belt replacements, an idler tension pulley is levered away to relieve tension on the belt and then belt can be removed and new installed.
You need to loosen the belt tensioner first off. This will give you the slack to pull the belt off with your hands alones. Make sure that you have the correct serpentine belt and its faced towards the correct direction. Re tighten the belt tensioner so the belt gets to the correct tension
