Go to the MIT App Inventor website, sign in if you haven't already, and get to the beginner tutorials via the menu at the top of the page (Resources--> Tutorials on the main page, Help--> Tutorials otherwise). We'll familiarize ourselves with the interface with the built-in tutorial for "Hello Codi" just to see how those work. This method does things like name the app for you ("HourofCode" in this case), gives step-by-step instructions on the left side of the screen and preloads 3 media files to use. There are 16 steps for this first introduction because we skip the "how to connect" section. We also skip Step 8 - that's when they actually connect to see Codi on their device.

Our desktops are not on WiFi, so getting the tablets connected to the internet doesn't help us. We'll finish the app and then build, download, install and test the app on our tablets at the end of the tutorial.

The last couple of steps are for installing the app on the device itself, which is why they included an image to serve as an icon. You will use PNGs with transparency like the one you already have of your 3D model, your Simple House or even a custom one you make with  your initials using the blending options Photoshop has so it can be distinctly legible. (Use things like a bold font, bevel and emboss, outer glow, stroke... you've got skills!)