IMPORTANT UDPATE: The Processing 2.x version of Unfolding has issues with the SimpleMapApp example and is not fully compatible with Processing 3. If you're using Processing 2, you should still be fine if you just use another example. If you're using Processing 3, you should use the beta version of Unfolding here: http://services.informatik.hs-mannheim.de/~nagel/GDV/Unfolding_for_processing_0.9.9beta.zip. Just download and unzip the folder, then place it in Documents > Processing > libraries. Then restart Processing.
Eventually that beta will become a full release available on their website (http://unfoldingmaps.org/) so if you're reading this more than a month or two after March, 2017 you might want to check there first.
Working with APIs, XML and JSON
NOTE: Since the recording of this video, Last.fm changed the overall sizes of their images. I'm now using the "medium" size instead of "large" as stated in the video. This change is already in the code linked above.