How to send a secret chat on wizz?

Here's Wizz app and I'm a bit confused how to send a secret chat. If I want to send a chat, standard chat; I understand, super chat; you will stay on top of their list, then there is bulk chat; your chat will be sent to the next hundred profiles.

But if I want to upgrade, it just says all secret chats revealed. But how do you send secret chat in the first place? I have no idea actually. I just know that if you upgrade, you will see that. If you know more about it, just leave it in the comments.