Log into your CPanel web hosting control panel and navigate down to the Domains section. Click on Addon Domains - enter the details for your new domain then when you have finished click on Add Domain.
Note: you must have already purchased a Domain Name in order to add it. If you do not have a domain to add you can purchase one through your client area. You will not be able to add a domain to your hosting if your package does not allow it - you can purchase add-on domains which allow you to add a domain to your existing web hosting space, from within your client area.
Note: you must ensure that your domain is pointing to our namesevers - these will have already been advised to you. Currently