You cannot work on files in TFS source control without a TFS workpsace. When you login to TFS for the first time, Teamprise creates a default TFS workspace with the name of your computer. You can remove this workspace and create a new one, or edit the name and give your workspace a name of your own choosing. (You will probably want to choose a different name.) For guidance on workspace naming and naming rules, see the User Guide section, Naming a TFS Workspace.
To create a new TFS Workspace complete the following.
From the workspaces drop-down menu located in the Teamprise Explorer window menu bar, select Manage workspaces...

The Manage Workspaces dialog displays the default workspace name assigned at login. It will also display any workspaces you previously created. Select the default and click Remove to remove the workspace. Click Add to create a new workspace.

The Edit Workspaces dialog is empty when it first appears. Type a workspace name and include a description of the workspace in the comment field. Note: Do not worry about the greyed out fields. Teamprise derives these values automatically from your comptuer. Click OK.

The Manage Workspaces dialog displays the new workspace. You can add another workspace by repeating the process above. Click OK to exit and return to the Teamprise window.

When you have finished this step proceed to the Adding a working folder mapping to a TFS workspace for instructions on specifying the working folder mappings in your TFS workspace.
You can remove a workspace by simply selecting the workspace in the Manage Workspaces dialog and clicking Remove. This removes the workspace and any mappings between local and server files that you have created. It does not however remove the files from your computer; you will need to delete these in the file system. When you delete a workspace and its mappings, any active directories in source control are returned to the inactive, "dimmed" state. When you only remove the mappings but not the workspace, files may still appear to be downloaded in the Source Control view. See the Troubleshooting Workspaces of the User Guide for further assistance. To make a directory active again, you will need to create a new workspace and add a new mapping.
Related Tasks:
Naming your TFS workspace
Adding a working folder mapping to a TFS workspace
Switching TFS workspaces