Let's take Filezilla FTP client to show how to upload backups :)
1. Get your FTP details and fill the required fields. Host field represents your FTP IP, Username - your FTP username, Password - your FTP password, and Port - the FTP Port. For example:
2. Click Quickconnect and, once you're logged in, locate your website's files from your computer on the left side of the program and open your hosting server's public_html directory on the right side.
Now you can drag-and-drop files or compressed archives from left to right, and they will be uploaded to the server! :)
Where to upload files?
Make sure that you are uploading files into the directory public_html under your domain name. public_html is a root folder for your website, so all files should be placed in it (unless otherwise specified by your CMS requirements, for most popular CMS like WordPress, Joomla, OpenCart, etc files should be placed into the public_html).
NOTE: If you upload a compressed file, you will need to extract it via File Manager.