You'll need:

• Tampermonkey[chrome.google.com] If you're using chrome
• Greasymonkey[addons.mozilla.org] If you're using firefox
• Violentmonkey[addons.opera.com] If you're using opera

This guide is created for mass group collectors, if you are not one, don't waste time for this.

Once you've clicked install, you'll recieve a notification (at least in Firefox) of the successful install however, not all browsers will do so but it's quite obvious if it's installed. But you can go to the page of the plugin to make sure that it's installed.

There may be situations in which you've not joined everyone group this person is within. This can be caused by the fact that some groups are private. Also, sometimes the script may not detect all of the groups. So do not forget to refresh your page a few times.