Can not access interface from my portable project to my iOS project. Simple SQLite example

I am following this tutorial and I am stuck on Step 4: Add the iOS Implementation.
http://code.tutsplus.com/tutorials/an-introduction-to-xamarinforms-and-sqlite--cms-23020
the code https://github.com/tutsplus/Xamarin-SQLite

I cannot extend to ISQLite ": ISQLite"
Prior to step 4, I have placed all of sqlite based files in the portable project and am placing the SQLite_iOS file under the iOS project.

I am using the Xamarin Forms portable app and am using the right packages. I am not sure what I am missing.