Can't preview my ibook on my iPad!

Hi,

I'm working on iBooks Author and I need to test my book to see how it looks like, before proceeding even more with writing.

What I did:

1- I downloaded iBooks on my iPad.

2- I connected it to my Macbook pro, using Mountain Lion 10.8.1

3- I clicked on "Preview" button on iBooks Author.

The problem:

Both device name + preview buttons appear to be greyed out.

What should I do?