What now?

I just bought a gold membership. I currently do not have any version of trainz running on my system. I don't seem to be able to download it from the trainz portal. Do I now have to buy it? What is the latest version? The system (trainz) seems to think I already have it. I can download SP4 but that's no help. There is no info listed with the Gold Membership to get up and running. This is a hell of a way to run a railroad.

Do the FAQs on the Membership page not help? You should also have received a confirmation email with links. You do not need to purchase anything - that's the whole point of membership.
MyTrainz should provide you an option to install both TRS199 and TRS22 (beta). Your Gold membership then provides the extra features when you log in to Trainz.
TRS19 SP4 is 114800
There is a beta version which you can patch to using the TRS19 Beta stream to 116009
TRS22 Beta is 115985

goto MyTrainz https://www.auran.com/planetauran/portal.php
and login, in the links on the left click "My Digital Downloads"
you should find a link to download TRS22 on that page
you could grab the online installer which is a very small download, run it, do the login and select your installation folder and since your a gold member select the "Trainz Plus Beta" Stream to download the latest beta version
or you could download the full installer which is 9.6GB and currently the same version as the Trainz Plus Beta stream (115985)
hope that works for you, have a good day!