I don’t believe this is in Monzo right now, there are no references to it in any client side code I’ve found and I’ve never seen it outside of mockups in presentations at least.
All you can really do right now is add your Monzo card to the usual contactless.tfl.gov.uk website and see your journey history there.
Side rant: I do wish that would stop appearing in presentations until it’s at a point where it’s working, there are so many other great things about Monzo that work today and as a rail and public transport fan, I see a few issues with the feature that need to be fixed TfL side first. Android Pay can only do a similar feature because they have direct access to contactless communications and the precise location simultaneously and in real time.