Workplace Join for Windows 7 is for domain joined machines, which means that we support the Professional SKU and above.
There is also no UI for Workplace Join on Windows 7, it is designed to be deployed and configured by administrators as part of desktop management solutions.
Once deployed, a scheduled task that runs at user logon will complete the Workplace Join on the users behalf, as you can see in my demo Win7 machine:
Events are logged so you can see results:
As with Workplace Join on Windows 8.1 and iOS, a certificate is installed onto the device, which is presented when AD FS conditional access policies are enforced to require device registration (i.e. IsRegisteredUser = True).
To leave the Workplace Join, you run this command:
%ProgramFiles%\Microsoft Workplace Join\AutoWorkplace.exe /leave
Note however that unless you uninstall Workplace Join for Windows 7, the machine will rerun the scheduled task at next user logon.