Installation Guide for Firefox Dev/Nightly (Patreon)

Enter the following url in the address bar of your browser:
about:config 

enter the following:
xpinstall.signatures.required

Double-click on the row that appears to set it to false.

From this point the process to install and update the extension is the same (If you update, do not delete the previous version, so you will keep your configuration).

Go to extensions or enter this url in the address bar:
about:addons

Go to extensions menu and drag the extension you downloaded for Firefox (zip file) onto the extensions screen.

Wait a few seconds, and when the window appears click on add.

Now you must go to the character.ai website, and on the extensions button at the top right allow the extension to work on the website:

Your extension is now loaded and ready to enjoy!