CTF Input key?

New to HTB here. I created a team and I want to participate in a CTF event, but when I try to sign up, I need to give an input key. Where can I find that?

That key means the CTF is private. Most of the CTF events HTB runs throughout the year are. The main public one for anyone that I’m aware of is Cyber Apocalypse. There are is also a Business and University CTF targeting those demographics specifically.