This of course applies to the AVR related Studio.
I have just realised that, unlike AS4, there doesn't seem to be different section for header files and C files.
Looking at a START example I can see that they are thrown in together like this (my attempted port of a program)
AS4 has them separated, notice the separated folders for each
Obviously I don't get how to separate them, do I create the 2 folders and add files there?