The unverified domain is added. The contoso.com page appears showing your DNS information. Save this information. You need it later to create a TXT record to configure DNS.
Add your DNS information to the domain registrar
After you add your custom domain name to Azure AD, you must return to your domain registrar and add the Azure AD DNS information from your copied TXT file. Creating this TXT record for your domain verifies ownership of your domain name.
Go back to your domain registrar and create a new TXT record for your domain based on your copied DNS information. Set the time to live (TTL) to 3600 seconds (60 minutes), and then save the record.
Could take up to 72 h, give it some time.
It took 10 min