Resizing images for blender in photoshop?

I remember seeing a tutorial someplace on the web, but can’t remember how I found it. I’ve tried changing image size, and saving, but that doesn’t save the new image size, I have a feeling I’m just not seeing what it is is something simple I just haven’t seen yet, but cs6 is my first new Photoshop since Photoshop 6. Maybe I mean making it so that they’re reasonably even, don’t know the word for that.