What program are you trying to use to edit your photos?
To make the photos physically smaller where they don't take up the whole screen, usually, there is an "image" selection in the toolbar and you can find a "resize image" somewhere under there on the drop-down menu. Don't choose "resize canvas" or you'll open a whole new can of worms.
Anywho, usually, I resize mine to about 400 pixels wide. In most programs, it will automatically adjust the height accordingly.
If you need more help, let me know what you're using to edit with and I'll see if I can figure it out for you.