Hi @Charlie29 , it sounds like the user might have been referring to a userscript, which are third-party tools created by other users, not by WaniKani ourselves.
Since they’re third-party, we typically don’t provide advice or troubleshooting on how to install them, but it looks like the thread for the script is here. There’s some instructions there and I’m sure anyone in the thread will be happy to help you out if you run into any trouble.