Why can't I customize my store's theme after adding it?

[CoPetSupply]

When I add a theme for my store it does not let me customize the current theme, it just says, "Manage Branding", I do have a subscription if that would've been one of the issues. How can I edit my theme or how can I fix the problem?

[CoPetSupply]

I didn't have a custom theme, just the original. I'm trying to use "Dawn". 

[CoPetSupply]

How??

[CoPetSupply]

Doesnt let me send 

[Shinonwrld]

It says manage branding , it doesn’t let you try to change it to anything, I’ve had multiple shopify stores and this is a first , can’t do anything