To Resize the Image

From the display window's Edit menu, choose Size.
The Size Image dialog opens.

There are two fields: X Resolution and Y Resolution. Each can be specified directly or, if the two fields are locked, a change to one field results in a change in the opposite file, thus maintaining the image's aspect ratio.
Key in the desired sizes.
Click OK.
Note: You cannot specify a size larger than the working size of the application window. If a value larger than this is entered, the image is scaled to fit in the application window.