.. How do I follow the directions?

You'll need two papers you should have in your inventory: a note from Magnus called "Chart" and a note from Lawrence called "Cave Map."

Where do I find all the journal sections?

Once you get to the ice caves, follow Magnus's directions as far as you can, then follow Lawrence's directions.

Here's a shorthand version of those same directions:

Ice Cave Directions, Part 2

At this point, you're looking at a wall of ice. Save, then break it with the hook.

Surprise! It's -- well, you'll see.

How do I deal with the culprit?