Cropping
Cropping an image refers to repositioning an image within a frame.

To crop an image,

To learn about frame resizing, click here.

See below to learn how to use the gridlines on the frame and the "rule of thirds" to help you better position your image.

Fine control
Mouse-down and drag a crop handle with holding the 'Ctrl' key will increase the precision with which you can crop the image.

 
If the crop handles do not appear
Frames can be placed into Image and Element modes.
Elements cannot be cropped and thus do not display crop handles.
 

Panning
To pan an image -- meaning to move the image within the frame --

1) Move the cursor over the pan handle in the center of the image.

2) Press and hold the left mouse button.

3) Drag the mouse around until the picture is positioned as you like it.

When you are satisfied with the new position for the image, release the left mouse button.

You can press the 'esc' key to abort the drag if necessary.

Note: you cannot move the image more than its maximum width or height. Learn more about aspect ratio for more details

From Wikipedia: "The rule of thirds is a compositional rule of thumb in photography and other visual arts such as painting. The rule states that an image can be divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines. The four points formed by the intersections of these lines can be used to align features in the photograph. Proponents of this technique claim that aligning a photograph with these points creates more tension, energy and interest in the photo than simply centering the feature would."

Use the gridlines appearing on selected image frames to help you position your image within the frame.
Click here to learn more about this helpful design rule: http://en.wikipedia.org/wiki/Rule_of_thirds