Take a look over at the far right of the Function bar. See the little icon that looks like a picture hanging on a wall? That's the gallery of graphics and sounds, decorative elements that can be inserted in your document. When you click the picture (or select Gallery from Tools on the menu bar), the gallery will open up with a sidebar on the left, listing the various themes.
Wander through the collection until you see something that suits your document, then simply drag it into your document, just as I did with that globe at the end of this paragraph. To banish the gallery, just click the icon again.
While you were using the Gallery, did you notice the words New Theme… at the top of the category sidebar? Click those words (which is really a button), and you'll be able to create a new category of images, clipart, or sounds. If you've got a directory of images you've collected, enter the path to that directory, pick a name for this collection, and you are done. Next time you bring up the Gallery, you can select from your own custom collection.