I wouldn't recommend starting on Windows Phone, since that's dead. Instead go for Windows 10 UWP apps. You will need Windows 10 to do this. Here are some points I'd start with.
Get a developer account
Instructions can be found here.
Get your PC ready for development
Go to Settings > Update and Security > For Developers and turn on Developer Mode.
Visual Studio 2015 Community Edition
This is the IDE you'll probably want to use.
C# and XAML
These are the languages I'd use. You can find a tutorial here. There are also tons of samples here. If you're willing to spend quite a bit of money, the C# Learning Path by Eric Lippert ought to give you a very good understanding of the language.
You should also read Microsoft's guidelines.