This will record a fragment of audio into that loop. It will immediately start to repeat, according to the master tempo and the channel's loop length. You have to turn on the filter to hear it. The Reference section below tells you what each control does. This will present a dialog box to read in a Looper setting.
Looper includes five demos.
They are very simple, I just threw them together to demonstrate a couple of possibilities. There are many more. The rest of the documentation describes how each control in the Looper window works. There are three sections, the Master Controls, the Loop Channels, and the Automation. This sets the master tempo for the Looper.