Hi @metacreator and thanks for your query. The Tobii Core SDK (which is .NET C#) is included as a Nuget Package which you download via the Visual Studio IDE package manager.
A full guide to getting started is available @ https://developer.tobii.com/consumer-eye-trackers/core-sdk/getting-started/
with a number of sample applications to help you get up and running @ https://github.com/Tobii/CoreSDK
Should you wish to remain with C++, then you can use the Stream Engine API which operates at a lower level than the Core SDK and so requires more expertise to use, but you can view the getting started guide @ https://developer.tobii.com/consumer-eye-trackers/stream-engine/getting-started/ which include download links at the bottom.
Please don’t hesitate to get in touch again should you require any further assistance. Best Wishes.