You have to create a club, and be administrator of the club. After you are administrator (or admin for short) you go to live chess and you can open tournaments all you want. The first step A.K.A the first sentence, is very hard to do. I don't know how to make a club, but I'm sure other people know how to.
How to make a Arena?

How to make a Arena?
As mentioned, first create a club.
https://support.chess.com/article/125-how-do-i-create-a-club
Then set up a tournament and change the Tournament Type to Arena
https://support.chess.com/article/1205-how-can-i-create-a-live-blitz-bullet-rapid-tournament

how do you make your own arena/tournament without any clubs involed?
You can't. Daily tournaments can be created without clubs.

I created the club but I want to make a blitz arena tourny OPEN TO ALL. How do I do that? It must be possible because they exist. I'm the only member of my new club, 3-2 Blitz Arean Club. Join it if you want.

You have to create a club, and be administrator of the club. After you are administrator (or admin for short) you go to live chess and you can open tournaments all you want. The first step A.K.A the first sentence, is very hard to do. I don't know how to make a club, but I'm sure other people know how to.
i do. if u need help, just ask me
How to make a Arena?