how do i realign drum after fitting drive belt?

i have just had to fit a new drive belt to my dryer. (hotpoint vtd00) i have reassembled dryer but the drum is not sat square and i am not sure what to do. the front of the drum seems to sit in housing but the back is hanging down and doesnt seem to slot into anything. i was thinking that the belt supports the drum and once started it would correct itself but it does seem a bit out and i dont want to try this incase it goes bad. thanks in advance. andrew h