adding new spells to a witch familiar

[Outland King]

So the text for the witches familiar says it can add additional spells using some ritual. Here was the actual text.

" A witch can also add additional spells to her familiar through a special ritual."

What exactly is this ritual? Can they use scrolls for this? What about wizard spell books? And do they pay a s riding cost like wizards?

[Manwolf]

There are a couple ways here to learn from scrolls, at the cost of the scroll and the ritual is described there, or other witch's familiars.

[Cavall]

Personally I just took pages, ground them to a paste and fed them to my magic flying cat pet. She didn't mind and fiber is good for you.