Implementing In-App Purchase

I'm trying to implement in-app purchasing in a Rift app I'm developing in Unity and have followed the applicable guidelines here: developer[dot]oculus[dot]com/documentation/unity/ps-iap/ 

So far, I've successfully uploaded a .tsv file for the item I want to sell, which will allow the user to purchase access to a bonus scene, and am now ready to try to write the necessary code.

In the guidelines, under "Integrating IAP", there’s a list of the available SDK methods, such as “Retrieves all of the user’s purchased items”.  But I’m not sure which SDK method I should use in my code.  I wasn't able to use the sample script in the guidelines to achieve my objective, although maybe I'm missing something.  If anyone can assist me I’d appreciate it!