Please follow below steps to upload files via the cPanel File Manager.
Step-1: Login to your cPanel account and Click on “File Manager” under the FILES section.
Step-2: File Manager will Open, Now Navigate to the directory where you want to upload your files to. If you want to upload your file to the public_html folder, you need to go to /public_html first and Click on the Upload button to upload your file.
Step-3: Once you Click on Upload a new window will open and Click on the “Select File” button and select the file you want to upload from your PC or you may drag also. The upload process will begin automatically and you can see progress.