To join a domain from a workgroup. Click Start, point to Settings, and then click Control Panel. Open System in Control Panel. Under Computer name, domain, and workgroup settings click Change settings.On the Computer Name page, click Change. Under Member of, click Domain, type the domain name, and then click OK. When prompted, provide a valid user name and password.When prompted, restart your computer to apply the changes.o join a domain from a workgroup. Click Start, point to Settings, and then click Control Panel. Open System in Control Panel. Under Computer name, domain, and workgroup settings click Change settings.