This is a great site, but the code hasn't been updated for a while. Viewing the VR scene on your laptop/desktop won't be a problem, but to get the code to work properly when you view it on a mobile phone in a viewer like Google Cardboard you'll need to make a slight update. When you remix any of the code examples in the tutorials, look for the section of code at the top of the index.html page that looks like this:
The text in red is the address of the version of the aframe library that's going to be used in your code. Replace the number 0.8.2 in it with the number 1.0.4
This should give you a version that works properly when viewed on a mobile.