This guide will explain multiple ways to manage your server files:
Built in web file manager. This method is the file manager that is available via the panel.
This method is only recommended to use for quick changes such as modifying a config file or uploading small files.
Using an FTP program, we highly recommend using FileZilla. You can download FileZilla here: FileZilla - The free FTP solution (filezilla-project.org)
You can find your SFTP credentials on the "Settings page" on the panel.
Guide on using FileZilla here: