For this example, I'm going to use "accountdomain.com" to represent your primary account domain name and "newdomain.com" for the new domain you want to park or addon.

Parked Domains - Parking a domain just points the new domain name to your primary account domain. So, if you were to park "newdomain.com", it would point to the same directory that "accountdomain.com" is pointing to.

For parked domain

1) First you have to update the nameservers of the domain which you want to addon
to your main domain nameservers

2) After updating the nameservers it takes 24 - 48 hours for dns propagtion, after dns
propagation login to your cpanel ==> Parked Domain

Addon Domain - This is usually the most sort after option. Adding on a domain makes it appear as if the new domain is hosted on it's own account, even though the files are still located under your primary domain. If you were to addon "newdomain.com", a user browsing to your site will see "newdomain.com" in the URL, but it will be redirecting it to a specific folder under your primary domain.

For example:

www.accountdomain.com/new would be the folder I setup for www.newdomain.com. Whenever a user browses to www.newdomain.com, they will only be able to see the files within the www/new/ folder on your account.

How to setup an addon domain:

   1. If you registered your domain with someone besides fastwebhost, make sure that the name servers are pointing to your maindomain nameservers  and wait a full 48 hours before proceeding with the rest of this.
   2. Login to your  control panel. (Check your welcome e-mail for login credentials). www.accountdomain.com/cpanel
   3. Click on the "Addon Domains" menu option under "Domains and Stats"

      Complete the form as follows:

          New Domain Name: newdomain.com
          Username/directory/subdomain name: new
          Password: apassword

      Whatever you put in the "Username/directory/subdomain" name will be the folder that is created under your primary account. It will also be the default username for mail and FTP.
   4. If the propagation from Step #1 is complete, typing in www.newdomain.com should then work.

Note : 1) First you have to update the nameservers of the domain which you want to addon or park
to your main domain nameservers.

2) After updating the nameservers it takes 24 - 48 hours for dns propagtion after the propagation you can add or park the doman with out any problem.