I don't see this unit on the Hoover support site. However other Powermax vacuums come up in the search for manuals: http://www.hoover.com/CustomerService/manuals/Default.aspx
Most of the units have very similar belt replacement procedures. First unplug the vacuum. Then press the handle release lever and place the handle in the low position. Next remove the hood by turning the two slots either side of the hood with a coin. Rotate the hood towards the front of the unit and remove it. Then remove the agitator brush roll and the old belt. Discard the old belt.
With the lettering to the outside, slide the new belt over the motor pulley. (The old belt should have been on the pulley. If the belt broke and isn't in place, look for it on the right as you look at the front of the vacuum above the agitator brush roller's position.) Slide the agitator brush roller through the belt and place the belt in the belt guide on the roller. Grasp the agitator and put it into position. Fit it into the rectangular slot on the left. Then pull it into position on the right side of the vacuum. Check if the agitator and the belt turn freely and that the belt isn't pinched between the agitator and the bottom of the unit. Replace the hood by aligning the tabs with the slots on the base. Then turn the coin slots to secure the hood.
I hope this helps.