Are you legit or did you download a CHEESE copy and now you want a key?
(Im sorry for posting the filtered word...didnt know...changed it to cheese)
If are legit...
If you have a laptop,it is usually on the bottom of the laptop...flip it over,write it down,enter it in the boxes(for activation probably)
If you have a desktop,your computer came with a book,on the bottom of the book there should be a upc code type thing and some shiny stripes...look at the numbers,write them down...enter them in the boxes.