Click the red App Menu icon >> Account >> Other: Affiliate Settings >> Manage
Copy the yellow highlighted link - that's your Affiliate Link.
Email your link - anyone who signs up and starts paying for an account will be credited to you.
You will receive 20% of the revenue gathered from anyone who signed up with your Affiliate Link.
Note: You can change your link by clicking the Change Affiliate Code link, but we do not suggest changing your link after you've started sending out to others as anyone with the old link would not be credited to you if you have not already signed up.