I hope I understood your question correctly, but it sounds like you’re wondering how to create the .generated.h header files.
The .generated.h header files are generated automatically for you by Unreal Header Tool (UHT). They will be generated whenever you declare a USTRUCT() or UCLASS() type in your header files. The name of the generated header will be the name of your header file, plus “.generated” appended. For example, if your header is called MyHeader.h and declares one or more UCLASS or USTRUCT types, the file MyHeader.generated.h will be generated for you.
The contents of the .generated.h file depend on the details of your type declarations. They generally contain glue code for run-time reflection, serialization, default constructors and initialization code.