in-app purchases question

I am trying to implement in-app billing into my app and i have been trying to follow the sample app along with the documentation but it a little confusing for me. I want t开发者_开发百科o be able to unlock parts of my app such as certain preferences but I am not sure how to check to make sure it has been bought and then how to enable it.

I have a purchased database like the example shows but as far as going to enable the extra features I am not sure what to do