In the front of the dryer between the top and the front panel there are two clips one on each side. Use a putty knife to release them and you should be able to lift the top up.
On the inside of the dryer you will find screws holding the front panel on. Remove these.
Slide the belt around the drum and put the screws back in.
Then go to the back of the dryer and put the belt on the motor pulley. | 
Dryer, belt replacement 
