# 1. Add a subdomain & verfiy
#### Add a subdomain to the customer tenant and verify it
* In the Microsoft 365 admin centre, go to Setup > Domains > Add domain.
* In the Enter a domain you own box, type the FQDN of the subdomain for this tenant.
* In the example below, the subdomain is sbc1.customers.adatum.biz. Or (\.sbc.cebodtelecom.com)
{% hint style="info" %}
Below is the FQDN that has never been registered in the tenant.
{% endhint %}
Click Next.
In the next step, you will need to verify the domain. Select Add a TXT record instead.
Click Next, and note the TXT value generated to verify the domain name.
Create the TXT record with the value from the previous step in carrier's DNS hosting provider.
Enter DNS record and Click Save.
Go back to the customer's Microsoft 365 admin center and click Verify.
On the next page, select I'll add the DNS records myself and click Next.
On the Choose your online services page, clear / untick all options and click Next.
Click Finish on the Update DNS settings page.
Ensure that the status is Setup complete.