Hi @NatalieLuengas,
What you'd be technically looking for is embed code which you'd have to paste into the Canvas rich content editor in HTML mode. There are a lot of technical "gotchas" around displaying a website within a website though, and many official Canvas integrations will not attempt to do that sort of thing because of the issues. I'd personally advise to just use a standard text hyperlink in the discussion, even if it requires users to click, as it's a much more universal solution that will work on any device/browser.
I hope this info helps you out a bit!
-Chris
