We'll assume that you can find a map of Japan and then find Hokkaido on that map. Hokkaido is the big thing at the top (the wide part). Here's a map of Hokkaido itself though:
This is Hokkaido, with north being at the top of the image. Hakodate is in the south, on the funny-shaped part. It lies on a body of water, the Tsugaru Strait, which separates the island of Hokkaido from the island of Honshuu. The city of Aomori is just across the straits.
At least most days she is. That's where she goes to school and does a lot of shopping and sightseeing.
Don't worry, I have better maps of Hakodate. This is just an overview. Click on the links below for very large closeups of parts of Hakodate. Many of the places shown on these maps are mentioned in toki's journal entries...it's almost like being there!