How to upload files to subdomains and Addon domains?
Uploading files to subdomains and addon domains are similar to upload files to normal domains. Just check for the folder names which are assigned to your subdomains and addon domains when you created them.
These folders will be inside public_html and upload the files directly to those folders instead of uploading to public_html.
Note: You can also move files to those folder, it works just as any other normal folders in your file manager.