According to UESP, after you finish chapter iv and speak to Hearmus Mora it says:

Once the conversation has ended, you may choose from one of three powers emanating from the Black Book:

Dragonborn Flame
Dragonborn Force
Dragonborn Frost

But I can't choose one. The book has 3 glowing green circles, but I don't know how to select the Dragonborn Force.

You cant mouse over an orb and press E on it? Also, the orbs dont 'float out' from the book?