C++ Builder 2010, add folder to project

I am sorry for this "beginner" question, but I am not able add directory with the existing 开发者_Python百科source code to the new project created in C++ Builder 2010 (that I am using very rarely).

I tryied to drag the folder to the project manager. The question "Would you like to add selected files to project" is displayed and and after confirmation nothing has been done...

I am not able to force C++ Builder for adding whole folders ( the files only...).