I am having a hard time visualizing this.
It's like putting a snowmobile belt on, you get it most of the way then spin the secondary clutch by hand, which is directly attached to the track (so it's easier if a helper can lift the track off the ground, same way it's recommended to have the trans in neutral), and work the belt over the lip and onto the clutch, or in this case the pulley. The socket on the pulley bolt allows you to spin the pulley and work the belt over the lip and into the groove slowly.