Resizing An Image at Photoshop.Com
Select Resize in the Left Tool Pane
Then click the Custom along the top Tool Bar
Then Type the desired pixel dimensions for the width, the height will change accordingly.
When its as you like it Hit Finish in the lower right hand corner of the window
Remember all changes are done to copies of the original image. So you can always go back to how
its started if you don't like what you did editing.