I do this in my experiences with a popup. First make a popup in the 2D section of your experience. Then back in 3D select the model or model item you want to touch to show this popup. Drag the "Click" event handle onto the popup in the tree.
Then select "Show Popup" as the action.
Now when you touch/click that 3D item it will show your popup. This is the simplest method. If you have a lot of items you want info on you are going to want to use some JS to change the text you show rather than creating a separate popup for each item.