Where to add items on Samsung In app Purchase Iap

Question

I have tried to use the SDK Iap since more than a week but I’m stuck in the first steps I have no idea how to move on. Im using the last version Iap6Helper. I have imported this module to android studio and added the dependencies, but what should I do next? Lets say I want to sell two consumable items : item a & item b.

where should I add those items on my code? is it on “ItemDefine.java”? or on another class? how to launch the buying of item “a” or “b” with just a click? My questions may appear like for someone who didn’t try to experience the Iap6Sample, but believe me I really tried very much to understand the code for days, but I couldn’t find a solution, my level isn’t very professional, I also couldn’t find online solution on other sites or videos. Thank you for every help I really appreciate it.