GM Common API (GMC) is a simple library designed for easily adding Greasemonkey 4 compatibilty to existing userscripts
Sometimes you can be lucky and few "mechanical steps" using GMC can fix a userscript. But in many cases you need a little more than that, and GMC is primarily targeted developers. I have tried to describe how to use it on the github page, but it still easiest read if you are a developer: https://github.com/StigNygaard/GMCommonAPI.js
As an end-user, if you cannot convince the userscript developer to make the script compatible with Greasemonkey 4+, I suggest you try using Tampermonkey instead of Greasemonkey to run your scripts.
How to
Hello, I am not a programmer so I have know idea what to do with this script to get it to work with Greasemonkey. Where, how do I put this script. Could you give instructions please for us that aren't programming smart? I would love to get some of my scripts for greasemonkey working again especially my award counter in Flickr. I have a group. I use Firefox, Windows 10 .
Thanks for any help