There's two options.
1. Login to cPanel, click "Filemanager", navigate yourself to the folder public_html (webroot). In the nav bar at the top find the button upload. This option is best for compressed zip packages. The filemanager can then extract the content of the .zip file, make sure the content ends up in public_html.
2. FTP, if you do not have an ftp client,
filezilla is an easy to use freeware client (make sure to chose the client). Once you have that installed, use the following information to connect:
Host: Your main url
User name: your cPanel user name
Password: your cPanel password
Make sure that you upload your content to public_html and no other folder (if you want it visible on web).