If you have Premium Shared Hosting, the following options may be available to access your website files and make changes. The options available to you will depend on the type of website you have, since Premium Shared Hosting is configured to maximize security for each type of site.
Content Management System
If your site is built using a content management system (CMS), like Joomla or WordPress, you can make changes to your website using the administrative interface. By default, FTP access is disabled on these types of sites.
FTP
If FTP access is available for your site, you will be able to use an FTP client, like FileZilla, to access and edit your website files. Make sure that the FTP client is configured to use SFTP, which provides an additional layer of security.
Troubleshooting
In some cases, antivirus programs on you computer may conflict with SFTP connections. There have been issues with the following programs:
Norton Anti-Virus - issue was fixed by going to Settings > Firewall > Program Rules. Find the program you are using to access FTP. Change the setting to Allow.