I'm using the paper_lantern theme in cPanel.
Go to Addon Domain and you will need to put your parked domain in the new domain name box. Then you need to create a subdomain.
Your document root is the folder where all of your files will now be.
Once you have done this, you will need to go into your file manager and move all of your files from the xxx.x10.mx or whatever address you have to your new
www.whatever.com folder
If after creating your addon domain it did not automatically create a
www.whatever.com folder in your file manager then you will need to manually create it.
example: public_html/
www.whatever.com