Kindly follow the below instructions in order to register a domain in Office365

2.Go to Admin center.
3.You can start domain registration directly from the dashboard by clicking on “Go to setup” or by clicking on “Domains” under Settings.
4.Click on “Add domain”
5.Enter the domain (ex-helpdesk.ae) name you want to register and click “Next”.
6.You will be provided with a TXT record to confirm ownership of your domain.You need to add this record in your dns zone.
7.Login to cp.buzinessware.com and go to “Domains”
8.You will see all the domains under your account.click on “view”
9.Before making any change in the dns records make sure that you are using default name servers for your domain i.e (ns3.hostinginuae.com,ns1.hostinginuae.com).
10.Go to “Manage DNS” in order to add/change dns records.
11.Add the required TXT record and click “SAVE CHANGE”.
12.Now go back to the Office 365 admin center and click on “Verify”
13.On the next page click on “I’ll manage my own DNS records”
14.You will be provided with a list of DNS records to be updated in your DNS zone.
15.Go back to cp.buzinessware.com and add all the records listed above and click “SAVE CHANGE”
16.Now go back to office 365 admin center and click “verify”
17.Your dns records will be verified and you will receive a message as below.
18.Your domain is now added in your office 365 account.
19.You can now go and create users/email addresses with the newly added domain.