You have two options if you wish to add non-recipe pages to you cookbook.
If you want them in the front of the cookbook, go to the Project Information Editor Tool in your editor toolbar and you will find options for "Cookbook Message" 1, 2 and 3. You can add text and images here and they will appear as separate pages in the front of your cookbook (hint: each message can be more than one page if you want. Just keep adding content.)
The second option is to use the custom page editor. This will add a section to the back of your cookbook.