How is the drive belt replaced on a Snapper riding mower LT200?

The drive belt goes from a pulley above the PTO on the bottom of the 20HP Briggs and Stratton engine, and then from that pulley going back is strattled around the steering column, then through a tensioning pulley and around the drive axle pulley. There are belt retainers on the engine pulley and the tensioner pulley. I am not sure how to get the belt off and back on.