Be sure your league is setup properly before installing any scripts.Setup Video
The directory contains the files for 2 different types of ways to swap between skins and color themes for you league.
The custom folder contains information on how to create different color schemes for your custom designed sites using CSS variable and local storage to save the themes for any user. This method can be challenging and you need to do some research on variable in CSS but i will get you started with an example.
The mflSkins folder contains the files needed to swap between any MFL skin. Each user can quickly change their skin and save it. This skin selector is only used for leagues using any MFL default skin.