[Togainu]

When you add a blessed spellbook to your character. You get greeted by a dialog box where you can associate it to a class and the spells in it.

Pick the class that the book will be used by. Lets take Wizard for example. The text to select from the dropdown will say "show these spells in my wizard spellbook"

Next add some spells (Lets use a level 1 spell "Deja Vu" as an example and select how you obtained it free, scribed, etc).

Afterwards click add. (at this point when you try to prepare your spells you can select spells from the blessed book but the spellbook button does nothing but bring up the create starting spellbook and adding new spells are done in the magic tab with the hammer/wrench icon)

--This is optional--

Now lets assume you haven't added a spellbook yet. When you click the spellbook button on the wizard tab now. You will be greeted by a dialog to add a starting spellbook. Do so by clicking the "Add starting spellbook".

After you done this you are greeted by the screen you normally see when clicking the spellbook. In this list you can also see the spells that are in the associated blessed book. Depending on how you added them they are in the "free spells in Spellbook" section or "Other spells in Spellbook". In this case you will be able to see "Deja Vu"

Now when you add a spell to prepare these spells will show up there as well to pick from.