Use an FTP program like FileZilla to navigate to the folder where you installed MediaWiki.

Opens the "skins" folder.

Locate the file for the skin you are using. The file for the default skin is MonoBook.php. Save a local copy, and a backup copy too.

Open the file in Dreamweaver, WordPad, or your favorite code editor.

Find the tag and paste the customizable Reftagger code from the Reftagger page right above it.

Save the file and upload it back to your server.