Not sure what you mean by "profile"...can you elaborate on what you're looking for please?
If an airplane is not already internally supported by GSX, it *requires* creating an airplane profile before you can use it in GSX. The DC-3 is surely not included in the GSX internal database, something you could have checked by opening the Airplane customization editor, which would have said the airplane is not already pre-configured.
In this case, before you can do anything with GSX, you must create a configuration for it, by setting all doors and other connection points correctly.
I suggest reading the relevant part in the manual, called "Airplane Customization", which starts at Page 51.