Import Samples into Garage Band

Hi,

My apologies if this is a loaded question, maybe someone can direct me to a tutorial.

I'm attempting to load samples into Garageband 10 for Mac. Every tutorial I've found is telling me to go to Smart Controls, click the Inspector button and load instruments via AU plug in.

The problem is, I don't see an inspector button where it's supposed to be and when I click on plug-ins there's no options for instruments. Am I doing something wrong? I have an MPK mini that I am trying to use with Garageband.