How do I replace belt on my Tumble Dryer White Knight WK247?

I bought a new belt for my tumble dryer which is slighty smaller then the original belt by probably 1 cm. I took the back panel & the top panel off the tumble dryer and fitted the new belt around the dryer over the old wear marks, but the belt was slighty too big! It fits but it doesnt fit snuggly as it should.Is there some sort of clip that it should be going into to make it tighter?