Requirements for DNS to ENS Integration
There are only two steps required to prepare a DNS domain for usage within the blockchain leveraging the ENS protocol. These steps are relatively straightforward for most users who may already be familiar with adding DNS records to their legacy domain names.
Two Required Steps for DNS to ENS
- Enable DNSSEC for the DNS domain

- Create a domain verification record (TXT record) set to an Ethereum wallet address

For detailed instructions see: DNS + ENS Guide - Connect a DNS name to the ENS Protocol
Fees to ENS-enable a DNS Domain
There are no registration fees to enable a DNS domain for use on the blockchain with the ENS protocol. DNS domains that have been ENS-enabled have available to them ENS functionality such as secure & decentralized records, the ability to set multiple cryptocurrency payment addresses, unlimited subname creation for different identities, avatar support, and to assign the name as the Primary web3 username/identity.
To learn more about the differences between ENS-enabled domains names and .eth names, see Imported DNS Compared to ENS Native .eth Name