As it is with dodgeball teams, so too is it with Tango Workspaces: you need an invitation to join someone else’s.
If your team is on a Starter plan, anyone in the Workspace can add you, as long as they haven’t hit the 25 member cap.
If the Workspace has been upgraded to Pro, you’ll need to have the Workspace admin invite you to the Workspace.
To make things simple when you ask, here’s a Tango on how to add someone else to a Workspace:
2. Click on Your Workspace…
3. Click on Workspace Settings
4. Click on Members
5. Click on "Invite Members"
You can also see who you've already invited on this screen under Invites.