To enable the Domain verification, we must require the following details before proceeding
Valid domain from a DNS.
FB account with Page and Business manager.
Firstly, log in to DNS and Business Manager and proceed to the Brand safety section in your Business manager.
Enter your domain in the add section, and choose the type of verification of your choice.
In the DNS section go to manage DNS and then proceed to add records section.
In the Adding records, add a TXT record with host as "@" and the value as provided by FB in the domain verification tag.
Please refer to the below video for more details.