Log into your website's cPanel and then click on the icon that says "Backup" (under the Files category). Then you will see a square button that says "Download a Full Account Backup". Click on that and then a backup page will appear.
Make sure your backup destination is "Home Directory" and click Generate Backup. This may take a few minutes. When it's done, your backup file will appear under "Backups available for download" on the same page. You will have to either refresh or go back into this page for it to come up. Then download the file to your Google Drive, Dropbox or computer!