Hello everyone I'm trying to activate enviroment hub but I still can't

I resistered in this link to get an Enterprise Edition https://developer.salesforce.com/promotions/orgs/dx-signup​​​​​​​
and tried to test it but I still cannot see the option. I'm not sure where I need to configure to see it

1. Can we have a free account for environment hub?
2. How much is it for account that support for environment hub?

Thanks all!

What I need to activate Environment Hub? 
I can't see the option in any place

I have a trial version of Salesforce Professional Edition. 
I need to have other edition to use it? 

Thanks!