Extension Support topic : Re: Not working in phpBB 3.3
The author poster that link and installation instructions can be found on GitHub.
As always with any non-validated extensions, always take a database backup before installing it (in fact I do that even for validated extensions).
I've had a quick look at the changes and I'ld take the risk installing it.
Should something go wrong: (I doubt it) : restore the database you just backuped, delete /production from /cache and clear browser cache and you should be OK.