You don't need to dowload anything.
If you have a version of window with Microsoft Photo Editor then do the following:
1. Right click on the image you wish to resize.
2. You should get an option on the menu "open with" left click on this.
3. Another menu appears with "Microsoft Photo Editor" (MPE) in it, left click on this.
4. MPE opens with you image. In the toolbar at the top you will see an option "Image", left click on this and another menu drops down. In this menu you will see an option "Resize", left click on this.
5. Another window will now pop up which will allow you to resize your image in cm inches or pixels. Remember to "Save As" at the end so you don't over-write your original.
If you don't have Microsoft Photo Editor, you will have "Paint" find this in the same manner.
Then from the toolbar click on "Image" then "Strech/Skew" , reduce the Horizontal and Verital Stech Perentages to get a smaller value and "Save As"