In order to copy a picture of the entire screen which can then be pasted into any application that accepts images, i.e. Excel, Word, Power Point, etc. just click the “PrtSc” button and subsequently press “CTRL” + “V” in the application where you want the screenshot to be pasted.
To copy a picture of the selected window rather than the entire screen press “Alt” + “PrtSc”.
To manually select part of your screen and copy the selection you can use the “Snipping Tool” which you can find in “Start” – “All Programs” – “Accessories”