The process begins by selecting a Windows Phone Marketplace category that fits your idea. Next, you add images, videos, and RSS feeds, which will become your app's featured content. Finally, you choose a color palette, generate live tiles, and splash and lock screens. App Studio glues everything together and comes up with something that works right-away on your WP-handset. It also provides the source-code, so you can take it to your IDE and develop it further.
At this stage, Windows Phone App Studio seems to be more of a working concept than a marvel, although it can be useful for creating a basic foundation for an app. But Microsoft's effort shows potential - the more powerful App Studio becomes, the easier it will be for developers to get into Windows Phone and help the platform compete for attention. At 12 million transactions per day and a selection of over 200 000 apps, the Windows Phone Store is a nice little business. However, it has to catch up with Android and iOS, which offer over one million apps each. This is a giant undertaking that also depends on market share, but there's no reason to be pessimistic. Windows Phone has gained a visible momentum this year, and it's set to increase its presence across 2014.
You can try Windows Phone App Studio yourself via the source link.
source: Windows Phone App Studio via WMPowerUser