How do you access the belt on the electrolux

Flip the power head upside down and look for 5 black screws recessed in the bottom of the head...2 mid way back and 3 along the brush area. Once removed the lid should lift off. Be careful not to disturb the wiring harness.
The brush roll has a pulley and bearing end. Both should be cleaned and any hair or thread removed. The motor screws will have tensioning positions for the new belt so leave enough slack so the new belt depresses slightly. You will find a replacement at vac shop or thru AERUS Electrolux dealers