Deck designs differ depending on the model application so the information for a specific deck is normally in the owner's manual for the tractor itself and not in a separate deck manual. There may also be a decal on the deck, or on the tractor just above the deck, that shows how the belt is routed and where the tensioner pulley should be.
Your Manage My Home profile did not list what model tractor you have so it is difficult to be more specific but you can check for the tractor manual online at Manage My Home for more details.
On the home page of Manage My Home, hold your mouse over the square labeled "HOME" in the upper left of the page and choose the option "Products and manuals" from the drop-down menu that appears. (If you already logged in, go to the red tabs on the upper right of the page and click the Magnifying Glass icon instead.)
Then enter as much information as possible in the search options. If nothing is found, check your product information for errors such as misspellings and be sure you have used only numbers and letters in the model number (no spaces, periods, etc.). The product might also be under another one of the "Category" listings.
If the manual can't be found there, please call the Manage My Home Member Services Team at 1-800-803-6775, between 8 a.m. and 8 p.m. Central Time. They will be more than happy to help you track down the manual.