Now, some theme comes with existing page and of course you want to delete the page as it is unnecessary for you. To delete the existing page,
1. Go to wordpress Menu > Pages > All Pages
2. You will see a listing of pages.
3. Mouseover on the page that you want to delete, click on the “Trash” link
4. Your page is then, deleted. To double check whether the page is deleted or not, go to your Online Store and check on the menu. It should be already gone with the wind.