The Addon domains feature allows you run serveral websites from a single account.
The main difference between Addon domains and Parked domains is that these don't have to be pointed at the root of the domain.
You can have a domain called myhostingaccount.com and then point domains at folders with in the account.
eg mysecondwebsite.com could be pointed at
Enter the domain you are going to addon to the account into the first box without http://www. prefix.
In the second box you enter the folder in your account you want it to
be mapped onto.
In the Password box you allocate the password or the folders FTP .
N.B. Addon domains may need to be turned on by your system administrator.