You don't.
The closest you could get would be to use an
<iframe>
or
<frameset>
(deprecated!) on your site to display the third-party site inside your own site, with your banners around it.
But most sites will prohibit this using
the X-Frame-Options header[
^], to stop people from doing precisely what you're trying to do - display
their hard work surrounded by
your ads.
There is no way around that. If the site doesn't want to be embedded in a frame on your site, there's nothing you can do about it.
The only option you would have would be to link to an interstitial page on your site, with your banners, a summary of the real page you're linking to, and the link to the real page.