1. From "home page" scroll all the way down to the bottom. On the bottom left you will see "Gift Cards" above the Twitter, Facebook logos. Click on that.
2. It will redirect you to purchase "Gift Cards", and each gift card can not be over $200 so if it is you will just have to do one for $200 and add to the cart and then whatever else.
I hope this helps. It took me a few minutes to figure it out as well.