This particular problem drove me crazy. There's a series of newsletters that needed to be placed in the site, and so I placed a File Cabinet in the page and uploaded the files. I learned that the files are automatically arranged based on File Name, which was not much help because the documents had the months included in the names. Therefore the titles were arranged as such:
It would be great if we can arrange the files too by date uploaded but no success.
The best way then is to rename the files. In my case, I wanted to keep the original file name because it is part of the organisation's naming convention. And so what I did was to add numbers instead.
To rename your files, click
More Actions > Manage site
Manage Site page appears
Click Attachments at the left hand sidebar.
Files uploaded to the system appears
Tick the checkbox beside the file you want to rename and click the Rename button above.
Click the Rename button when done.
Do the same procedure for the rest of the files.
Return to your File Cabinet page and refresh.
PS I'm keeping track of this Help Forum just in case Google Sites update the File Cabinet features