You can activate Origin keys bought from GamerAll with the following two methods:
 
Method 1. In the Origin client.
  1. Log in to Origin with the EA account you would like your game added to.
  2. Click on the Origin menu on the top left.
  3. Select "Redeem Product Code."
  4. Enter the serial key from the back of your game manual.
  5. The game will be added to your "My Games" section of Origin.
After download is finished you are ready to play.
 
Method 1. On the Origin website.
  1. Go to www.origin.com/account  
  2. Log in to your Origin account using your Origin email and password.
  3. Select "Redeem Product Code" in the left-hand menu.
  4. Enter your product code on the Redeem Your Code page.
In second case scenario you still need to wait till your game is downloaded and available in the Origin client.