Description from extension meta
Swap between Twitch chat and Kick chat without leaving Twitch.
Image from store
Description from store
Kick Chat for Twitch adds a simple toggle button to every Twitch channel’s chat panel, allowing you to flip between the native Twitch chat and a fully functional embedded Kick chat box – all without leaving Twitch.
Once you have added the extension click the extension from the drop down and login to Kick, If it doesn't work/tells you to login to Kick then make sure you allow all cookies on Twitch and Kick and try again.
The Kick chat will default to whatever Twitch channel you are currently on, if their usernames aren't the same on both platforms then you can edit the Kick chat username by clicking the pencil icon next to the toggle button, this will be saved on that specific channel.