Board Thread:Support Requests - Getting Technical/@comment-995176-20190108231324/@comment-9605025-20190110011934

You import the script using your wiki's MediaWiki:ImportJS (help page). The line you would add is dev:CategoryIcon/code.js This has been explained on the page Fngplg linked to.

As for window.fng.cicon, I am guessing that your need to create that in MediaWiki:Wikia.js. There is an example on the page that was linked to.