To get to Options and preferences in Amazon Apps:
1) Press the menu button from the Amazon Apps home screen
2) Select “Settings”
From this page you can sign in with your Amazon Credentials, Redeem a Gift Card to the Amazon App store and set your preferences regarding Connection-type (if you prefer to use Wi-Fi when application file sizes exceed a certain limit) and Notifications (when you prefer Amazon Apps to generate notifications in the notifications toolbar).
Since application purchases are tied to a certain account, logging into Amazon Apps from a different Amazon account than the one you use to purchase your application will affect your ability to use those applications.