No manual - how to replace belt?

Question

Hi, I bought the (appropriate) replacement belt for a DirtFINDER (not self-propelled) but don't know how to put it on correctly as a) the belt was broken when I removed the cover plate, b) I've never in my life looked at the 'inside' of a vacuum cleaner, and c) the machine is a couple of years old and the manual is long lost.
Thanks for any help!