How do I put a belt back on a Murray lawn mower?

Question:Has a 42 inch deck 16.5 hp model # 313777 It has totaly come off and I do not the first thing about lawn mowers or pulleys or belts.

Answers:
You'll have to go to a small engine repair shop. I went to murray.com and here's what they say:

There are no models matching the model number '313777'. Please make another selection.

Please be advised:
--Murray products older than 2003 model year are no longer supported. This includes any paper or electronic manuals.
--Murray parts older than 1996 are no longer supported. This includes any paper or electronic parts lists.
--Active Outdoor Products (such as go-karts, sleds, mini-bikes, etc.) are no longer supported.