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 host name, 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! :)
NOTE: If you upload a compressed file, you will need to extract it via File Manager.