Zooming in and out of an image (enlarging or reducing the image on screen):
1. Select the "Zoom" tool (it looks like a magnifying glass).
2. Click on area of image you want to bring closer. Notice that there is a "+" sign on the cursor, which now looks like a magnifying glass.
3. If you "draw a box" around an area with your mouse, that selected area will fill the entire window.
4. To zoom out, hold down Alt (Windows) or Option (Macintosh) and click on image. The cursor will have a "-" sign on it.
5. When you have enlarged an image as much as you can the cursor will be blank.