Since not everyone has a photoshop program, here's how to do it in paint.
-Open the image in paint
-At the top left of the screen, click where it says “Image”
-Under Image go to “Stretch/Skew” (Ctrl + W)
-Then under Stretch (the first two boxes) change the horizontal and vertical percentage (100% is the original size of your picture. If you enter 25%, it will be 25% of the original size, not 25% less than what it is now)
-MAKE SURE THAT YOU TYPE IN THE SAME NUMBER FOR BOTH HORIZONTAL AND VERTICAL
-No need to dick around with Skew
-If you find the image isn't the size you want, go to “Edit” then, “Undo” (Ctrl + Z) and enter in a different number (Image is too small - larger number) (Image is too big - smaller number)