Add a year to my current 360 license

Norton Security | Norton Internet Security
1

I have a one year key I want to add to my current 360. I have about two months left and want to extend the product. 

How do I add the year to my system?

2

I have a one year key I want to add to my current 360. I have about two months left and want to extend the product. 

How do I add the year to my system?