To switch to another workspace from the dashboard, click the arrow near the workspace name. Choose the workspace from the drop-down menu.
NOTE: If you just created a new workspace and you don't see it in the drop-down menu, it is because your default role is set to super administrator. Only contributors have access to the workspace. So if you want to interact with projects yourself than make sure you add contributor to the list of your roles. See how you can change roles.
If you want to see workspace settings, go to the Workspaces tab under your account settings. By default, Default workspace setting page will open. To change the workspaces, click the drop-down near the name of the workspace and choose the necessary one.