• Open your cPanel account and log in.
• Locate the Addon Domains icon in the Domains section by scrolling down.
• The following form is shown in the area that occurs.
• Type the name of the addon domain, such as newadomain.co.uk, in the New Domain Name area. 
• A subdomain is automatically generated for an addon domain name when you create it in cPanel. The subdomain name form is automatically filled up for you when you complete the new domain name section at the top. You can alter the subdomain name here if you'd prefer something else.
• You may create a new FTP account by checking the box that reads, "Create an FTP account associated with this Addon Domain," if you wish to use FTP to upload files to your Document Root folder. Upon checking this box, a new section is revealed.
• You will instantly be given an FTP username. If necessary, you can input a different one.
• Type the desired FTP account password in the Password area, and then type it again in the Password (Again) field.
• After completing the form, click Add Domain to establish the addon domain.