Just set up your main panel domain using these settings with your domain registrar's DNS: http://docs.sentora.org/?node=95
After doing this, you will be using Sentora DNS for all add-on domains, just point them to ns1.yourdomain.com and ns2.your domain.com and add them in Sentora using Domain module and DNS Manager module defaults.
After that everything will be running off Sentora, including mail.
Simple.
Once you understand what is going on there and have your DNS up and running, you can then change things around to cloudflare or whatever else you decide, or just leave it as is.
This will at least get you started.
Then read up on this doc to further setup and understand what is going on: http://docs.sentora.org/?node=53
