I'm adding ssl certificate using zero ssl They are asking to
To verify domain ownership using DNS verification, you will need to create DNS records of TXT type as shown below. Please remember that it takes some time for new DNS records to become "visible", so you may need to wait for 15-20 minutes before clicking "Next". You can check whether your records became visible with the following command: "nslookup -q=TXT XXX", where XXX is one of the records as shown below.
Domain TXT Record _acme-challenge.example.com
Value
string_removed_here
_acme-challenge.example.com
another string here
So what should I do here I'm using this blog but I think their verification steps have changed