Keep in mind that,
- Office 365 creates a default domain in the signing up process. If you want you can keep this domain or add a new domains to the service.
- Domain which is registered in GoDaddy is added in this scenario.
- Third party service provider GoDaddy is used to host DNS
Go to Office 365 Admin Center.. Choose Add Domain
Enter the Domain name…
verify domain (in this scenario GoDaddy is the domain registrar)
Log in credentials should be given to log in to GoDaddy
Update DNS settings..
How to check the newly created Domains
Go to Office 365 Admin Center —> Settings —> Domains