How do I replace the drive belt on a Yard Machine, 17.5 hp, 6-speed?

I'm trying to replace the small drive belt on a Yard Machine, 17.5 hp, 42" cut, 6-speed. What needs to be loosened or diconnectred to make this possible? After smashing my hands a couple times I decided it was time to ask for help. Any advise?? Thanks!