cPanel is not a site builder... it's a control panel to manage your domain, email, and other things.
cPanel's file manager can assist you in uploading files (like HTML files) which would be the pages you design. This can also be done through FTP.
Here's a test for you to try:
Open up Notepad on your computer and paste the following code into it.
<head><title>My First WebSite</title></head>
Save the file as index.html
Now log into ftp, or log in to cPanel and go to the file manager. Browse to your public_html folder, and then click the link to upload a file. Upload the index.html file you just created. And then go to http://yourdomain.com/
You should then see a very simple page with the title My First WebSite, and the text on the page should say Hello World.
Search google for html tutorials to learn more.