How do you create a "promo code" for an iPhone app

How you do you "create promo codes" for an app as given in the answer by David Maymudes (below question link)? Is there an iOS UI for it?

How to restrict application distribution to a group of users only via Apple AppStore?

Can you code an iOS app for free?

In app building, the tool you need is called Xcode. You can download it directly to your computer from the App Store. Once it's downloaded, you will use it to build your user interface and for writing code to respond to user interaction. And, good news: It's free.

Go to itunesconnect.apple.com. On the front page is a link to "Request Promotional Codes".