When you run the game you should see a Microsoft screen giving you the option to press X to download the latest version or A to continue without doing so. Be sure to press X and wait for it to download.
(I have to say that when I tried this, it got to 80% and then gave an error message "could not download..." I had to actually delete the game and go to the indie games section and re-download it. Then it worked. So their update process may be a bit flaky? Let me know if you had this experience too, although I can't do anything about a problem on Microsoft's end. Anyway if the update process fails, just delete the game and re-download it.)