I would like to see what the tail number is of the aircraft in flight tracking. Is this possible and I’ve missed it?
As has been discussed here many times and is clearly stated in the Questions/Answers (FAQs, available at the top right of every page in FlightAware), you cannot do that.
Some operators do use the registration as the flight number. These are mainly fractional operators. An example is EJA307 is a NetJets flight that is using an aircraft registered N307QS would be EJA307
There’s also antonakis.co.uk/acars.php?page=request