To join an existing Workgroup in Windows 10 do the following;
- Navigate to Control Panel, System and Security and System
- Find Workgroup and select Change settings
- Select Change next to ‘To rename this computer or change its domain …’
- Type in the name of the Workgroup you want to join and click OK
- Reboot your computer for the changes to take effect
- Navigate to Control Panel, Network and Internet and View network computers and devices to see other machines within that Workgroup.