Gandi.net

Log in to your hosting provider and find the "DNS Record" :

DNS Record

Select your domain name :

Domain Name

Add a first entry with a pointing field "NS" using the subdomain you previously selected in your GTM (e.g., xyzxx) and the nameserver URL "ns1.gtm-helper.com."

Add a first DNS record

Repeat the operation a second time for the same subdomain, with the nameserver URL "ns2.gtm-helper.com."

Add a second DNS record