There are three thin, veritcal ribs on the volute cover. You need to turn the cover counter-clockwise by using the plastic handles of the pliars. Spread open the handles & place each handle against a rib. Then turn the pliars to put pressure on the ribs & thus turn the cover.
I don't have a digital camera to show any better, sorry. If you can;t get it, look in the "Octo X Club thread" which is in the Lighting forum. There's alot of pages but a few weeks ago I remember someone posting some pics.
I subscribe to that thread & the "MSX X Club" thread for tips & mods.