Roller Brush. How do I install the roller brush. I didn't pay attention when I removed it

Question

How do I install the roller brush.  I didn't pay attention when I removed it and now when I attempt to vacuum my low carpet it doesn't seem to be working.  The green light on the head of the vacuum goes out when I click it down to the floor.  It didn't used to do that.  Plus I think I smell something burning.  Could the belt be broken?