How to open-up a Powercom IND600A UPS ?

My computer is attached to a Powercom IND600A UPS which does not charge properly. When the lights go out the UPS shuts of within 5 seconds. This has been happening for a week now. So my computer is at risk.
I think some capacitors are blown off thats why the battery won't charge. I think i can fix it cause i know a little about electronic devices. But i can't get the UPS to open up. I took off the 4 screws of the back panel, then the back panel comes off. But i can't take off the sides or the front panel.
So, if anyone has tried opening a Powercom IND600A or a similar UPS please let me know how should i get it apart.

I know i can call the Powercom service guy. But the ups is out of warranty. And the last 2 times he came over he charged alot.
Thanks.