What we need from you to link up your web domain to GROW for emails is:
Access to the service you registered your domain name with. It will likely be GoDaddy or Google Domains but could be someone else. We will copy over your existing DNS records to our service and change your NameServers to point to ours.
Instructions for getting us access if you have registered your domain name at Google Domains:
See this article on how to grant us access: https://support.google.com/domains/answer/7179397?hl=en
Instructions for getting us access if you registered with GoDaddy:
Shoot us your GoDaddy login (UN & PW) in chat support.