This Tag Groups Premium plugin is not available in the built-in plugin search of your WordPress blog. That means you have to manually upload the ZIP file that you have received. Fortunately, the process is very easy and you just need to click a few buttons.
- You need to be logged to your Wordpress blog as administrator. In the menu go to Plugins and Add New.
- On top of the page, click on Upload Plugin. You can press the button Browse... and select the tag-groups-premium-latest.zip file, or drop that file on the field around the button. Then you click Install Now.
- Then you need to activate the plugin.
- You will now find a new menu below the Settings, named Tag Groups.
Note: Instead of uploading the ZIP file, you can also uncompress it and upload the folder to your blog's plugins folder. This, however, is only for advanced users since you afterwards may have to fix file and folder permissions (particularly for files that must be publicly accessible).