The absolute easiest way to view a photo sphere on your phone is to create it yourself. Using Google’s Photo Sphere Camera (for Android or IOS). By creating your own spheres they are immediately on your phone. However, getting the side by side view for use with your VR headset can prove more difficult.
Google cardboard caught my eye in late 2014. I was not one of the first to know about the new technology, but I may as well have been. When I started researching the topic let’s just say information was scarce.