Are you serious?
Take your hands off your keyboard.
Open the case which contained the disc when purchased.
On the LEFT hand side (provided you opened the case the correct way around) you will see an instruction manual, perhaps more commonly referred to as a 'book' or 'booklet'.
Remove this 'book' or 'booklet' and read the back page.
If it has an activation code on there, enter it where prompted. If it doesn't, there may be a website you need to visit to obtain said code. Go to this website. Retrieve the code. Enter code where prompted.
If the code is neither on the 'book' or 'booklet' or on any website, I don't have a clue.