As you can see from the captured Polyspace example demo project [Help menu > Examples > Bug_Finder_Example.psprj] below, the header files in the folder containing the source C files are automatically included in the scan target. You can directly add header file folders in the purple box below, or you can add header files in Configuration > Environment Settings in the cyan box below.
In the above demo project 'Bug_Finder_Example.psprj', it has the option '
' as default 'source-headers'. It means that results appear on source files and header files in the same folder as the source files or in subfolders of source file folders. In the demo, it also has the option '
' as default 'include-folders'. It means that results are not generated for header files in include folders and their subfolders unless they are in the same folder as the source files. You need to consider these options together when you add include header folders/files.