Click the Deform Tool on the left side of the screen.

A gray box with handles (small boxes) will appear around the photo. Hold the shift key*and
   hover your mouse over the lower right corner of your photo until it changes to an "over
   corner handle". Click and drag it to the lower right corner of the canvas area. If the image
   doesn't fit vertically, you can continue to drag the image off of the canvas area. You will see
   how your image will be cut off. Hover your mouse over the image and move it where you
   want within the current canvas size.
An "over corner handle" looks like this:

*Holding the shift key maintains the aspect ratio (proportions) of your image.