|You will need a program to do this but don't worry, there are
many free ones on-line and almost every computer operating system
comes with one.
With your cropping tool, create a square around the subject in your
image that you want to crop, by dragging in a diagonal motion from
the top left to the bottom right.
Hit the Enter Key or use the button that completes the crop.
Now find the PIXEL size of the image, this is different from the
FILE size. The pixel size is the exact number of tiny colored "squares"
make up the image. Constrain the proportions if the option is available.
Find the Height and Width and set the one that is largest to 500,
if it's perfectly square then both height and width will be 500.