These are some resources that might help you with your sketchbook assignment. In addition to these, you might also look up commonplace books, smash books, and altered books.
Art Journals can be whatever you want to make them - all art, or art and text, or an illustrated journal or diary. These links are to videos, examples, techniques, and information that might help you.
- http://mindfulartstudio.com/how-to-start-an-art-journal/ - Tips for starting your first art journal
- http://www.createmixedmedia.com/make/journaling - Examples of journals, techniques, and tips for journaling. Lots of resources here!
- http://textmyjournal.com/art-journal-prompts/ - 30 prompts to help you get started in your art journal!