When you take pictures using a digital camera it normally saves the files formatted as .jpeg on a PC disk. The first thing you should do is copy the pictures from the disk you used in the camera to your computer desktop. This will allow you to work from a more reliable media source, as well as, speed up the editing process. The files will have names that make little or no sense to humans - we'll take care of that later. Open the file in PhotoShop - you will have to start PhotoShop first, then from the file menu open your picture.
Lets start by re-sizing the image.
A dialogue box will appear as shown below. Constrain Proportions is on so if you make any changes to the size it will happen proportionally. Change the Width to 200 pixels. You will notice that the Height will automatically change to 150. Click OK to see the results.