lawn mowers?

hi have found the belt has snapped in the mower having had to take it apart took nearly hr and 100 hundred screws later ???
am now trying very very hard now to work out how you replace the belt when you are unable to stretch it over the spindle and the drive motor at the same time when you have to close it completely way way over my head i suppose there is a way or it is quite easy but i cannot see it any body got any answers to it please ????? susanne