Hi,
The tutorial shows how to set up a project using the C API. The error you got is related to the C++-binding. The InteractionAgentBase is a simple utility class that registers an application as an EyeX client for the current process using a Windows API call to GetCurrentProcessId to get hold of the process id. You need to include the correct header for your Windows version to be able to compile it. Please refer to MSDN to find the correct header to include:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms683180%28v=vs.85%29.aspx