This small tut, is assuming you just oppened the page, didn't touch any button (press F5 to clear all)

1. Click 2 points at the white canvas
1.1 => You just made a BONE

2. Click the Button ADD+ FRAME (below Timeline)
2.1 => You just added one more KeyFrame to the composition
2.2 => On this new KeyFrame the bone you drawn can assume a new position

3. Click any edge of the Bone, and click again anywhere on the Canvas
3.1 => You have just setted a animation for the bone, very well!

4. Click PLAY >, to animate what you just created!
4.1 => That is a small preview, the possibilities here are huge!

5. To add a image as skin to the bone paste this: exp/marara.png at the field Image Url (under the Bone Panel) and click the ok button
5.1 => You applied a image to the bone, bounded by it's limits. You can add any valid Image Url there.