To add a subdomain in Groove:
1. Click your person icon in the upper right.
2. Choose Settings and billing
3. Ciick the domains tab
4. Click Manage
5. Find your domain in the list.
6. Go to the far right of the domain name and click the button: DNS
7. Click Add Record
8. Use the Type pulldown to choose Cname
9. Under Name enter the subdomain name you want to use. So if you want the subdomain to be news, type news. So in this example, the url would be: news.yourdomain.com
10. Under Content, enter the address the cname needs to be pointed to. For letterman, it would be: cname.letterman.ai
11. Check off: Enable cloudflare proxy.
12. Click Save