Step 1: To redeem an Origin key, you will require an Origin account and the game client, the Origin game client can be downloaded here: https://www.origin.com/nld/en-us/store/download And you can create an account here if you do not already have one by clicking Register in the lower left hand corner here: https://www.origin.com/
Step 2: Open the Origin game client and click the Origin menu in the top left
Step 3: Select "Redeem Product Code"
Step 4: Enter your serial code
Step 5: The game will be added to your "My Games" section of Origin ready to be installed.