Games downloaded from zynga.com:

• While each game will be slightly different, the update flow will start from within the game and prompt you to download the latest version with the tap of a button.

Games downloaded from Zynga Connect:

• Your game will be automatically updated if you have auto-updates enabled.  If you do not, you’ll have to open the Zynga Connect app and tap “Update”.  You can enable auto-update at any time from the settings menu.