Trying to install but can't

[tomcat335]

I recently got 3 Kidde smoke detectors and would like to add them to my HA. I tried using the instructions (although the screenshots didn't match what I had). I went to the store add on store and then repositories from the hamburger menu. I tried adding https://github.com/tache/homeassistant-kidde but it said that it is not a valid add-on repository.

Hopefully someone here can help me get it added. I'm also hoping to get a little help getting it to find my devices since I'm not quite clear on how to do that.

Thanks!