In order to submit the form, you'll need to copy the shape in the box, as indicated :)
Make sure to check out the plugin homepage to find out more about it, or watch the MotionCAPTCHA Github repo to be notified when the plugin is production-ready.
Ps. When not building realtime data interfaces or working on this, I'm writing about JavaScript, CSS, WordPress and a few other things on josscrowcroft.com. Check it out.