One other way that you can do it if you don't want to email them to yourself is to open them in "paint"
Go to where the picture is stored and right click on the name of it, then click "Open With" and it should give you a number of options including "Paint"
Then on the top bar you should see "Image" click on that. Then click on "Sketch/Skew..."
That should bring up a screen where you can change the horizontal and vertical size of the picture. As a default it should say 100% for both of them. Change them to at least 50% and click "OK"
Then click on "File" on the top bar and then "Save As" rename the picture and place it into the file that you want and you are done.
You can also rotate photos in the same program by selecting "Flip/Rotate"