remove a computer from a domain and join a workgroup, depending on your operating system and preferences.
Using System Properties:-
1- Go to Computer (This pc) Properties
2- Click on Rename this pc (Advance ) right side.
3- Click on change button in middle
4- Choose domain or workgroup as your requirement .
a- Domain - Enter domain name
b- Workgroup - Type any word (Workgroup)
5- then enter credentials
6- Restart the system.