The obvious answer is "Ask your friend" who is already familiar with your specific set-up
but in the meantime...
Your web host's control panel (of which cPanel is one type) is what you are looking for, but you won't actually see the database within the file structure...there is a separate section for db management within the control panel, usually named phpMyAdmin. You would probably also see MySql as a section - that's usually for setting up databases and users.
Your File Manager within your control panel will let you see the directory structure and access files, although editing files directly on the server via File Manager is not recommended.
To be absolutely sure about your database in use and access details, you need to locate the file in includes/configure.php and view it - the info starts at line 48.
Just to clear your mind on one point...the database does NOT store files. The files help you create data which is stored in the database, so you (certainly at this stage) don't need to worry about editing the db directly. To give you a (hopefully) simple example...
Your products have images, and when you enter product information via admin, you enter the information as to where to get the image from and where it is to be stored. Assuming you use the default, when you upload it, your image file is stored in the images directory; the exact location of the file is stored in the database.
When the image is to be displayed, one of the program files will ask the database where it is, and the database will reply with the location of the image, so that the program file then moves on to locate and display the image itself.
You should set up an FTP application (Filezilla is free) and download a complete copy of your existing site on your own hard drive, and do any editing there. Always use a text-editor such as Notepad++ or Crimson Editor for your editing; the likes of Front Page and Dreamweaver will create problems that your own limited knowledge will not allow you to fix; NEVER use a word-processor because they add all sorts of hidden codes which completely mess up web pages.
And now you need to do a LOT more reading, starting with the Tutorials/FAQ section.
Oh - and welcome to the most helpful forum on the Internet!