If you are logged into the account you bought the game with, there should be a download option on the top or the bottom of the store page. Alternatively you can look in your library to find the download option there.
Once you've downloaded the new version, copy all the files from your old save folder to the new version of the game.
If you are playing on Windows, open the /www/save/ folder of the old game version and copy all the files inside it. Then go to the /www/save/ folder in the new game version and paste the files in there. The new version should then have all your saves, settings and gallery unlocks.
If you are playing on Mac you can find a similar save folder if you look inside the Game.app file (without running the game).
