The green box labeled "CROPPED AREA" shows exactly what will be saved.
Move your image to position it inside the crop area and use the square handle to resize.
If your image appears pixelated or blurry: Start with a higher resolution image.
If your original image is portrait rather than landscape: You will have to drag the blue square quite a bit to enlarge it enough to fit. It is okay if the image gets partly cropped so long as important elements such as people's eyes aren't cropped out.
