Adding CNAME record for a domain with subdomain
In this case your custom domain will look like
calendar.yourbusiness.com
Log in to your Wix dashboard and go to Account Settings
Go to Domains section
Click on
...
next to your domain and select Mange DNS RecordsClick on Add Records under CNAME section
Add Hostname and Value
Click on Save
For more information refer official documentation
Adding CNAME record for a root domain
We cannot set a CNAME record for the root domain in Wix