1) Login in to the Cpanel account where the existing addon domain exists and confirm;
Cpanel > Domains > Addons
2) Backup the addon domain
Go to File Section: File manager > public_html folder > select the folder of the add-on domain e.g add-on-domain.com, right click and compress the folder selecting .zip as compression type, now right click and download the compressed file to your local machine.
3) Backup the database of the addon
Go to File Section: File manager > public_html folder > select the folder of the add-on domain e.g add-on-domain.com scroll down and right click on the wp-config.php file> select view > and get the details of the database username and password.
Now, navigate to ; Database > phpMyAdmin > select the database of the add-on > select export > select Go, and the file will be downloaded to your local machine.
4) Speak to your hosting provider to propagate a hosting plan for the existing add-on domain, this may take 24-48hrs depending on other factors.
5) Restore the addon domain to the new Cpanel
Once propagated, login to the newly created Cpanel of the add-on domain, Go to File Section: File manager > public_html folder > select upload > select the downloaded file from step 2. Upload the .zip folder, then reload and extract the .zip folder. Finally delete the .zip folder after extracting all the files in it.
6) Restore the database of the addon to the new Cpanel
a.Create a database
Go to Databases section: select MySQL Databases > input the database name of the file from step3
b. Create a new user and password
From step 6a, scroll down and on MySQL User> Add new user > input the database username and password similar to step 3 (for the sake of accuracy), and click create
c. Add user to the database
From step 6b, Scroll Down to the Add user to database section: input the created user and the database and click Add.
d. Now, Navigate to Databases > phpMyAdmin > Select the newly created database > select import > choose the downloaded file from your local computer in step 3 > and click Go.
7) Confirm that the new domain is functioning and the files and database are working perfectly.