There are several built in choices, or you can type over the old numbers. The first number is width, the second height, both in pixels. Leave the Preserve aspect ratio box checked, type in one number and the other will be calculated for you.
Resampling an image often improves its quality, especially when enlarging it. Resizing without resampling can result in a blurry image.
Note: the showed Resample filters are used for enlarging only. For shrinking, a special/fast resample filter is used.
Click OK to resize the image.
This action can be reversed by the Edit Menu’s Undo command.