The Straighten tool is easy to use.
Simply select the tool, click and drag a line where the horizon (or vertical) should be.
In the example, the line was drawn on the chests of the mother and son.

• Make sure Rotate All Layers is selected in the options bar.
• Also choose one of the following cropping alternatives in the options bar.
Because the photograph is going to rotate, the corners may no longer be inside the rectangle of the photograph, and white space will appear as well.
The canvas is expanded to fit the entire rotated photograph.
No part of the photograph is cropped.
Original Size: 1280 px x 1024 px
New Size: 1521 px x 1350 px
Crops the photograph to remove any blank areas.
Original Size: 1280 px x 1024 px
New Size: 929 px x 609 px
The canvas remains the same size as the original.
The corners of the photograph are cropped.
Original Size:1280 px x 1024 px
New Size: Same
If you haven't already done so, go to Saving Files.