Inserting a graphic that is wider than it is long means one of two things:
1. You have to turn the graphic so that it is longer than it is wide.
2. You have to turn the page so that the orientation changes from portrait to landscape.
To complete option 1, you need to know something about a graphics program like Picasa or Paint or any number of other graphic programs that allow you to rotate a graphic. Here's an example of a document that has been rotated.
Assuming you are able to rotate a graphic, you can then simply insert the graphic into a portrait page.
To complete option 2, you need to know how to create a Continuous section break, change your page orientation, insert the graphic, insert a second Continuous section break, and change your page orientation. Here's a sample of what the page looks like.
If you think I'm hesitating, you're not far off. I'm debating how much I need to explain about using graphic programs. In my own books, I prefer to use option 1 because the page layout isn't interrupted. All of my headers and footers are in the same place. However, I have lots of experience with graphic programs and access to high-end graphics programs at work.
Option 2 is often easier for a person who doesn't know a lot about graphics programs. However, as you can see from the sample page above, your page layout is disrupted. Instead of having your header and footer running along the top and bottom of the page, they are running along the sides of a printed page.
In either case, your reader is going to have to turn the book sideways to see the graphic. It's a matter of the location of your header and footer along with the page number that is the issue.
So I'm just going to stop at this point as I ponder what I need to do and say. We may end up taking a short trip out of Word and into Paint.