1. [Recommended step] Create a copy of the image you wish to resize. 

2. Right click on the image you wish to resize, scroll to Open with and select Paint. 

3. In the top toolbar, select Resize.

4. You can now resize your image to your desired size either by a) Percentage b) Pixels. Keep Maintain aspect ratio checked if you want the vertical proportions to change automatically after changing the horizontal such that the image remains the same aspect ratio. 

Note: You can undo changes with the button at the top left corner. 

a) Percentage: You can choose to reduce or increase the photo's size by percentage. 

b) Pixels: If you know the dimensions, you can choose a pixel size. 

5. Save the image by clicking the button at the top left corner.