Well, see if you can follow this.
Most photo editing software like Photoshop have a resize feature but don't like it when you mess about with the ratios so might now allow you to resize it to those exact specifications.
What you can do then - which is relatively easy with some intuition.
3264 x 2448
2592 x 1944
To change it to those specs, what you need to be doing is shrinking it both length and width wise.
With a little bit of arithmetic, find out what percentage of 3264 is 2592 and what percentage of 2448 is 1944.
Then open the image up in regular paint, Microsoft Paint in the accessories of your start menu.
On the tabs at the top of the screen, you have 'file', 'edit', 'view' and 'image' - choose 'image' and select 'stretch/skew' from the drop drown menu.
This features gives you the option to resize images by a certain percent, if you put down 100% for both length and width it remains the same size, 200% twice the size, 50% half the size and everything in between in terms of percentage.
The value you put in those boxes in the stretch/skew feature are going to be less than 100% of course because you're shrinking the picture.
so x% of 3264 is 2598
(x/100)(3264) = 2598
3264x/100 = 2598
3264x = 259800
x = 259800/3264
x = 79.5 or 79.6 roughtly 80 but stick to the smaller value of 79.
Now you need to work out the value for the second box.
(x/100)(2448) = 1944
2448x/100 = 1944
2448x = 194400
x = 194400/2448
x = 79.4 so again.
Bottom line,
Put 79% into both those boxes, to shrink it by that amount - to 79% of its normal size, so you see its going down in the same ratio there won't be any distortion and you'll have something that fits just fine.
Hope that was helpful.