Do you have Microsoft Photo Editor loaded? If you don't know, what program opens when you try to open a file with a JPG extension? (eg. picture.jpg)
If it's Photo Editor, open your file & choose 'Re-size' from the 'Image' menu. A box will open with options to either change size by percentage, or to 3.5 by 6.2 inches (just an example.) Just make sure the 'allow distortion' box is NOT checked.
You can then save it. I usually save it as "picture-small.jpg" or some such in case I want the original for something else instead of just saving over it.
If you don't have Photo Editor, you can PM me & I'll give you my email address so you can send it to me & I'll do it for you.
Deb