You will not only want example.com to work for you and your visitors but also www.example.com. Any probably others, like beta.example.com.
Why? Because some people, if you tell them to go to example.com, they will automatically go to www.example.com. They think it only works with www.
When you create a website in Boomla, you can use either form. There is no difference. Use whichever you like. Not sure? Just use the one without www, it's shorter. :)
Whichever you use, if visitors go to the other one, Boomla will automatically redirect them to the correct domain.
What about beta.example.com? In Boomla, you can clone your website to work on hidden versions, called branches. That's so that you are not breaking your live website that others can see. That would be uncool. So you create a beta branch on beta.example.com, edit it, then publish your changes. You may have many such versions, so it's better to point all subdomains to Boomla.
Add the following record:
||Hostname (or name)
|Hostname (or name)
Can not use *
Then use www instead of *.
You may want to create another entry with beta instead of *. You can create as many of these as you want, any time in the future.