Changing default directory for domain
While this step is optional in most cases, it is highly recommended you do this for security reasons. You should change default directory for your website content from root folder to public sub-folder. You should be able to do this from your cpanel.
After creating a database, unzpip the .zip file you downloaded from CodeCanyon and upload only "quizier" folder or sometimes called version number (i.e. 1.0.0) to your ftp root folder (usually called www, public_html, html or something similar) or even a sub-directory.
After upload, you should have something like this on your server:
Always use a desktop application like FileZilla to upload files to FTP as opposed to web based file managers to avoid issues with file permissions, corrupted files or not properly uploaded.
After uploading files, simply open up your site in the browser and follow on-screen instructions to complete the installation.