Now remove diffuser cover. It's held in place by 4 pairs of tabs. Squeeze each pair of tabs with needle nose pliers and gently lift that corner. After all the tabs release, you can lift off the cover. Don't tip the base or the door will fall out.
I only marked three tabs in the photo. If you can't find the fourth tab, then I know what you did with the beer that didn't fit in the cooler in step one!