First you log into your cPanel and click your username on the top-right of the screen. Then a menu will drop down; click the Reset Page Settings option. Your cPanel settings and look will then be restored to the original setup. It should now look the same as the first time you logged in.
To clean cPanel log in to cPanel. Under the FILES section of the cPanel home screen, select File Manager. In the File Manager Directory Selection dialog box, choose Web Root and click Go. Now, click Select All and then delete. Again, click Delete File(s).