How do I put a genuine factory parts deck drive belt O.E. 954-04062/754-04062 on 38"Bolen's lawn tractor model#13AM762F765

To start with, the easiest way is to remove the mowing deck from the tractor. It will really be tough if you don't or can't. You may need an owners manual to guide you through all the steps.
1. Remove the cutting deck from the tractor 2. Work the old belt off (if not broken) the mandrel pulleys and idler pulleys 3. Pull the belt away to reinstall a new one 1. Work the new belt around both the mandrel pulleys 2. Make sure the belt is in all the pulley grooves and inside all the belt guides 3. Now you have to reinstall the mowing deck. Here are some diagrams that should help you.
http://www.ereplacementparts.com/bolens-13am762f765-2005-lawn-tractor-parts-c-27272_27390_27402.html