Official Microsoft Bot Builder V3 SDK GitHub repository.
Clone the project or put these files in a zip archive under:
Documents\Visual Studio 2017\Templates\ProjectTemplates\Visual C#
Place Bot-Application.zip in the directory above and use it as a template:
File -> New -> Project... -> Visual C# -> Bot Application
You can get V4 template here:
Azure Bot Service Documentation
Create a bot with the Bot Builder SDK
Natural language understanding
QnA Maker API