I cannot download free app to my new air 2

According to this announcement Free Apple apps for your iPhone, iPad, and iPod touch with iOS 8 - Apple Support, we can use Apple apps free of charge with new Apple product.

I bought new iPad Air 2 last month.

Before use the new one, I installed my old iPad profile with iTunes.

But still I cannot install freely these apps to my Air 2.

What can I do to install these apps?

Thanks.