With that the manual means:

You have a Lite-C project and it's main file is main.c and now want to use and convert a C-Script coded file called materials.wdl to Lite-C. So you would want to create an empty file called materials.c and include it inside your main.c file. Then step by step port sth from materials.wdl to your materials.c file.

What you're trying to do right now isn't converting the code. You tried to include file.c inside file.wdl and call a Lite-C function from file.c!?