Https://www.partstree.com/parts/troy-bilt/edgers/tb516ec-25a-516-966-troy-bilt-edger-2011/general-assembly/


Zoom into the diagram, remove (item 45) belt cover to expose the belt and pulleys. Take note of how the belt is routed.! you will need to follow the same route with the new belt. You may need to remove the Blade guard (item 40) if the belt doesn't fit over the head of the guard. There may also be a sprung idle tension pulley, which will take up the slack in the belt once replaced. Looks pretty straight forward.