Right click on your picture. Go down the menu to 'Open With'. If you are running Windows and Office, use the Microsoft Office Picture Manager (you may have other picture modification software so look around your computer if you don't see this program.

Once the picture is opened, go along the menu bar to 'picture'. There will be two choices; 'Crop' and 'Resize'. Use the resize (I usually use the 'percentage' box) and bring down the pixels to a manageable size (400 X > ). Either rename the file under save as or do a straight save a just keep the reduced file.

Good luck.