You can create a backup of your site quite easily. Account backups can be performed using the cPanel -> Backups functionality for your hosting account. If your account is not too big in size (under 500Mb) you can perform a full account backup just with one click.
If the account is too large (over 500Mb) for the full automatic backup the files and the databases should be backed up separately. In this case you would need to know what your web site consists of and thus what should be backed up/restored. Sites consist of files and databases. You must take care of them all if you want to have your site exactly the way it has been before.
In order to backup your files, you should download all the files from your public_html folder to your computer using your favorite FTP client. After that you can easily upload back the files to your hosting account and your website will be restored.
Once having all the files on your computer, you should make a dump of your MySQL database. Click here to learn how to backup/restore your MySQL database.
You may also request an affordable backup creation of your whole account by posting a ticket from the Exclusive Professional Services tab inside your Help Desk area.