Domain Mapping ? - Subdomain same hosting account

Hi support. I have setup a wordpress mu on the main domain I have several add on domains that will be a part of the multipress network so I'm trying to map them. The issue i'm running into is when I map to it's showing the root directory of I'm guessing my answer lies in changing DNS setting but I wanted to ask first since the add-on domains are all on the same hosting account. Using Hostgator, Cpanel, shared server. Thanks!