You can create a custom index.html page by using Frontpage or Dreamweaver or simple HTML (If you know it) and then upload it using the file manager in cPanel(TM) or by using an FTP client. If you know HTML, you can just edit the index.html file in the public_html folder as manzoor has said. Please remember to set up the page within 7 days of setting up your account failing which you will be temporarily suspended.