Looking for the code currently in Nuget?
https://github.com/Windows-XAML/Template10/tree/version_1.1.12
If you want Template 10, just open up Visual Studio 2015 and search "Template 10" in the Extension Manager. After you install it, when you go File>New>Project the Template 10 project template will be in your list.
After you create a project, head to our documentation wiki and get started: http://aka.ms/Template10