Sizes

Silly Question......
if I want to print the image to put in a keyring how do I scale it down to the size I want? At the moment I can only do it either too small or too big for the keyring size. I cant crop it in windows as it says its not saved in right format?? I grab and share and use 16mp png.
Any answers would be appreaciated, thank you :)

Could you please send to support email a screenshot when Windows says that the image wasn't saved right?

Could you please go to Properties (of the saved image) and click "Unblock" in "General" tab and then try again?