Here's some info to help you Incase you don't know the series and maybe- I get you into the series before any spoilers in the chapters 😏
First of all I gotta show you the first 5 minutes of season 1 episode 1!
Sky is my oc! All mine! Jason and Mason are as well! Other than that everyone else is canon!
If you need to find a specific character whether you are new to the series or forgot something
https://avatar.fandom.com/wiki/Avatar_Wiki
Here's the wiki