Hello and welcome! I don't know the answer to your question on customizing a built-in skin. You can put site-wide CSS style code in your wiki's
MediaWiki:Common.js. If, instead of
Common, you use the name of the skin, the code applies only to that skin.
Please end your posts by typing ~~~~, which makes the wiki replace it with your signature and a timestamp.00:26 27-Jun-2020
Fake Wikipedia page?[edit source]
If the result is funny, you are welcome to create one at
uncyclopedia.ca! 19:48 7-Jul-2020