1) First Login with your Amazon ID to the Amazon.com
2) use below link
https://www.amazon.com/b/ref=relo..._i=balance
3) if your account is eligible, click to Qualify. ( YMMV)
4) Reload your balance.
How to Use Your
Promotional Code:-
Add one or more eligible products sold by Amazon.com to your cart.
The savings will be reflected on the final order checkout page if the items in your order are eligible for using the
promotional credit.
Complete your purchase no later than May 15, 2016, 11:59 PM (PT) and the
promotional credit will automatically be applied to your order.