Hi Abhi !!
you need to just create new html pages and add links to those page in existing webside,for this first you need to use any ftp tool so that you can download all the pages .
Then create new html pages,since these pages will be displayed whenever user click on the link,menu .etc ,so u need to create new links or provide menu options.
copy new html pages and changed files to the remote server.
Hope this will help you