how to display clicked pages in single iframe

You can change the src attribute of the iframe for each of the link. Iframe would load the content for those new locations and will display them.

For example, you can give this code a try,

<iframe src=""></iframe>
<a href="http://www.w3schools.com">Click me</a>

Inside the JavaScript script you can write this code to handle the events (navigation) and then display the document inside the iframe.

// Make sure you're having jQuery
$('a').click(function () {
  // prevent the page from navigating
  event.preventDefault();
  // load the page (located at the href of current hyperlink) inside the iframe
  $('iframe').attr('src', $(this).attr('href'));
});

This would handle all of the clicks on the hyperlinks, and will load the content of that page inside the iframe. Make sure that the page is visible (can be loaded) inside an iframe, for example, you cannot load Google's web page inside iframe.