I believe you just push it back on. I had no trouble with mine.
For some reason, I thought it said the screws were T4 when I read this yesterday, so I thought I was lucky when I found a screwdriver set at Home Depot today with a size that small (I would have gotten one with anything smaller if they carried one). I was momentarily disappointed when I opened this guide back up, but happy again when the T4 worked perfectly.
Is this guide wrong, is the label on the screwdriver set wrong, or are T4 and T3 known to be interchangeable?
I just ordered a replacement battery from this site. Looks they have quite a few replacement parts.