Computers in a workgroup network all need to have the same workgroup name. If you are joining your Mac computer to a workgroup network, follow these steps to set (or change) the workgroup name.
1. Using the Apple menu or the Dock, open System Preferences.
2. Go to the Internet & Network section and select Network.
3. From the left pane, select the desired network connection.
4. Go to the bottom of the right pane and click the Advanced button.
5. Select WINS from the horizontal menu.
6. Input the Workgroup name or use the dropdown to select it.
8. Close the Network window.