how do i thread the drive belt which has come loose on my Victa SPX2548 ?

how do I thread the drive belt on my Victa SPX 2548 ride on mower. A diagram of which pulleys which way would help. Do I need to 'force' the drive belt over the pulley withthe spring attached or is there a way to get it on despite the 'arm' that should hold the belt on in the first place?