Get set up. Visual Studio Express 2013 for Windows gives you everything you need to start developing apps.Instructions for getting set up
Get the samples
Sometimes, the best way to learn is to look at an example, so we've created hundreds of Windows Store and Windows Phone Store app samples for you to learn from. You can also download all the official samples at one time by getting the universal Windows app samples pack.
Online training for building Windows apps
Want to design and build Windows apps using XAML and C#? Learn to use the universal templates in Visual Studio to create apps that share much of the same code for Windows Phones, tablets, and PCs.
If you haven't done much coding before, but have a great idea for a phone app, start here. Bob Tabor's 9+ hour series covers developer scenarios to build outstanding Windows Phone 8.1 apps. If you’re completely new to software development, check out Bob's series on C# first.
Microsoft Technical Evangelist Jerry Nixon, and real world software expert Daren May, President of Crank211, a digital experience company, will teach you how to save time building apps or Phones, tablets, and PCs that share much of the same code base, using universal Windows app projects in Visual Studio.