How Do I Purge Users from My Workspace?

You will need to be an Administrator to purge inactive users from your workspace (users whose access has been revoked).

As an Administrator, click on your user name on the top right corner and select "Account Management."

From the Account Management page, locate and click on the "User Administration" button:  

The User Administration page will display a listing of users. You can click on the "Purge Users" button to remove ALL inactive users from your list. 

Here's an article explaining how to remove / revoke user access from your workspace.