How do you sample music to make a loop in Koala Sampler?

Grab audio from YouTube and start making music with this $5 app. Chopping up samples and making loops with Koala is easy, fun, and you can use any audio (well, not from a copyright perspective, but...) This video takes you through a few basics, grabbing the audio, trimming it to the right length, finding the BPM / tempo, and starting off the basics of a new track.