Use the potion on your pickaxe, then clear away the hunks of wood on the large disc in the center of the library. With those removed, you can now use the two nearby levers disc to spin the two outer layers of the disc.
Spin them until the picture of Princess Aurora is aligned like the photo above.
You’ll be rewarded with the Royal Net, which you’ll then have to use to catch flying Snippets around the library. This is easily achieved by pressing the corresponding action button when near them.
Speak to Merida again, then follow her instructions to clear each wing of the library of Snippets. When you’re done, chat with her once more, then head over to the Lorekeeper book.
Here, you’ll only be able to purchase one of the stories available to you using the Snippets you’ve rounded up, so go ahead and buy “Once Upon A Time In Storybook Vale…”