The Dryer belt tensioner is a little wheel on a spring assembly. If you have a good belt leave it in psition over the drum and hanging down to the motor pulley. Put the front and top back on. Do not even try to position the tensioner from the front.
Of course you have unplugged the dryer before you took it apart. Now move it away from the wall enough for access.
Next take off a little access panel (remove 2 screws) near the bottom at the back. Now it will be easy to move the tensioner past the motor pulley and under the belt. This will keep it tight. Close up, reposition and plug in your dryer. You are done.
John
September 2007