Hi,
In-Apps purchase is a great thing, but it just doesn't work out of the box. There are a few things you need to do before you can even test out the sample code.

Here is a video that shows how to setup a test app and then create In-App purchases with the identifiers (ProductID) that are used in your apps.

The video can be found at http://howto.oz-apps.com/2011/01/background-work-for-in-apps-purchase.html

The process is the same as creating an app on the iTunes store, the only difference is that you do not have to upload a binary.

A few things that were already created
1. A Unique Provisioning Profile
2. A 512x512 Icon for the new app entry, you can create a blank 512x512 image
3. a 320x480 image for the screenshot, you can create a blank 320x480 image

please leave comments and suggestions, this shall enable me to add.change this document.