The Auteureist™ Store is accessed from the About Screen, by tapping the Shopping Cart button.

The store will connect to the Apple App Store and retrieve information on available items and pricing. This requires connectivity and may take a minute.
The available plug-ins will be listed in the bottom half of the screen. Note this is a scrollable area..

Tap on a product in the list and you will be given more information about the product and its price.

Tap on the Buy button and you will be shown a confirmation dialog describing the product you are about to purchase.

Tap on the button with the Price to confirm your desire to purchase the product. You will be shown a final confirmation. Tap Buy to buy the product..

You will be prompted for your iTunes account information..

Enter the information and tap OK. After a moment or two, you will be shown a confirmation, and the Auteureist™ Store Screen will be updated to indicate the product is unlocked.