To install:
1. Download the plugin on ZotFile site: The download is an xpi file.
2. Open the Zotero application (the computer program, not the web extension), go to the Tools menu and select Add-Ons.
3. Click on the gear icon and choose "Install Add-on from file"
4. Locate your downloaded xpi file and click Open
*Note - If you end up using and enjoying ZotFile, please consider supporting the creator of the plugin by donating via the yellow "Donate" button on the Zotfile website.