The preview window shows your image with the original view on the left and the corrected image on the right. If you want to adjust the division between the original and edited image, click and drag the triangle below the image. You can also zoom in on your image to see more detail.
◗Click Apply to make your changes on the current “tab.” Your edited image becomes your new original and the slide indicators move to the center of the range.
◗Click OK to save the changes you made on all the Corrections tabs and return to the main screen.
◗Click Cancel to cancel the changes on the current tab and return to the main screen.
Cropping
If you want to save only part of your image, use the crop function to cut out the rest of the image. Follow these steps:
1Open the image you want to modify.
2Click one of the selection tools on the left side of your screen.
3Click and drag the mouse over the area you want to save. A dashed border indicates the area you selected.
selected area
4If you change your mind about which part of the image to crop, simply click anywhere in the image and repeat step 3.
5Click the Crop tool 
or choose Crop from the Image menu. The part of the image that was outside the dashed line disappears.