You can download ‘FastStone’ it is a free software that you can use to resize images.
You can download it from www.ninite.com
1. At the bottom of the page under ‘Imaging’ check the box for ‘FastStone’
2. Click the green button ‘Get Installer’, let is download on your computer and open the .exe file and run it
3. Open FasStone
4. In the left window browse to the folder where your image is that you need to resize and click it, it should show in the preview window
5. Click on the ‘Resize/Resample’ button in your toolbar and specify the width and height in pixels of your new image
6. Click ok and save your changes (make sure to give your new image a new name)