The answer is to turn the 3D image into a two-frame animated gif like the one above. By quickly alternating images you get the feeling of depth. And maybe a little wooziness, too. Welcome to the world of the wiggle pic. Here's how to easily make them.
Step 1: Get your files off your 3DS
Each picture you shot on your 3DS has a JPG file and a MPO file. What you want is the MPO file as that contains both the left and right image while the JPG only contains one. So copy the MPO files onto your computer.
Now that you have your files you have two options. One is quick and easy, but has no privacy or control. The other is the opposite. We'll cover the easy technique first.