Cropping allows you to isolate the portion of the image you want and discard the rest.
To crop an image, first click on the Crop Button 
on the Wizard Panel. A cropping
frame will appear on your image. You can reposition the frame by clicking
inside it and dragging, or stretch and shrink it using the adjustment handles
on the sides, until it encloses the part of the photo you want to keep. The gray area outside the frame will be
discarded.
Original image
Resize the cropping frame around the area you want to keep
Once your selection is in place, hit the Crop Image
button in the Wizard Panel to crop it.
Cropped image