An Sub-Domain is an extension of your existing primary or add-on domain(s). It can serve as a location for a website.
When configuring the the sub-domain it is either usable standalone (ie: kb.example.com) or fallthrough.
Selecting fallthrough Mode will set this subdomain to catch all the http/website-requests if no other domain or subdomain is matched).
Important: Before proceeding ensure your Domain NS-Records are set to the nameservers provided by MyRoot.PW
Add-On Domains can be configured/added in WEB > Sub-Domains. There are a couple of tunable parameters: