Theme forest never notified me of any new updates but I am trying to workout the slideshow glitch everyone else has been experiencing. Changelog only lists up to 1.5 but I am looking for the latest 1.7
ThemeForest does not notify users when there is new versions of themes. I would suggest you to follow Kriesi on Twitter and on Facebook :)
You should login on ThemeForest with the account you purchased Angular and go to Downloads section and simply download Angular.
For a quick guide on updating your theme take a look at this video on updating the theme via FTP: