I need to know how to change a mower drive belt on a 48 inch john deer riding mower

Remove the front belt guide from around the electric clutch, remove the belt guide from the tranny and loosen the idler assembly and replace.

I highly recommend getting the manual for this. I replaced mine recently first I got the wrong belt. Tractor supply gave me the wrong belt I put it on it was too short and broke then I went to john deere to get the right belt and it was cheaper than the wrong belt. Check both the mowing deck belt and the transmission belt mine has 3 total. Replace them all the first time and any idler pulleys that feel "rough" a bad pulley will eat a new $15 belt before you can say "i smell smoke"happy mowing

Always go with OEM. Never get a subsitute