Are you having issues with connecting via FTP? Personally, I prefer the the client Filezilla for uploading my files via FTP, however it is understandable if you use your own personal client.
When attempting to FTP you may come across errors such as 530 Authentication Error. This error references an issues with the credentials being entered for the FTP user.
If you are using a secondary FTP user on cPanel the format for the username should be (email@example.com).