Hi Ники,
In summary, it requires a backend. The forum post above has some information about setting one up.
We'll have a more thorough guide up soon. Thanks for your interest!
There is a demo up at Harvard, but I believe it is only for their internal development purposes. I'll let Rashmi respond as to whether she can make that available. The backend software has been slightly lagging behind front-end development, but we hope to have a public demo annotation server up at Stanford fairly soon. If you are really hankering to try it out immediately use this
index.html from a development branch which has a link to Princeton's temporary store, but don't expect to rely on it.