■ Install Tampermonkey extension first if you haven't already, then install this script.
■ Add skins by going to Settings → Appearance, and hitting the green + button. Enter skin URL into the box. Skin URLs can be found here: https://docs.google.com/spreadsheets/d/1xO8DTORacMmSJAQicpJscob7WUkOVuaNH0wzkR_X194/htmlview
■ Remove skins from your storage by pressing the trash bin icon on the right side of the skin.
■ If skin is flashing or otherwise not working, make sure you haven't put any additional space at the front or end of the box where you enter skin URL. Also make sure the URL ends in .png (or.jpg, etc.)
■ If you want to store and use animated skins as well, make sure to also add the animation script: https://greasyfork.org/en/scripts/385643-animation-script
■ Bonus feature: When multiple skins are selected, you can randomize your skin any time during, before, or after a game or practice mode using the Randomize key button. To set Randomize key button, go to Settings → Controls → Randomize skin. But in order to enable this feature, you must first have the animation script.