To see your workspace management options, go to Workspace settings at the top of the left sidebar. In the window that pops up to access the different sections:
Get your workspace's unique identifier
Configure the workspace avatar
Set a Name and Description for your account
Manage your Connections to any git provider or Salesforce.
Manage users and roles.
How to reactivate users
Open the Users management page
Click on the Status filter and select Inactive
Search for the user that must be reactivated
Click on the Status toggle
Select the User License