The sample projects are available here on github, there is one for C# and one for Visual Basic.

The sample projects are console apps - the entry point is Sample_Main.cs. In each folder of the sample project - including the root - there is a readme file with documentation. If you run the project it will produce some workbooks to a folder in its output directory. See the code for more details.

Clone the sample project of your choice and start exploring the code.