C as in cobalt source code. H as in header file? Something like that. And is this code written for the GP32, or for a normal computer?
Anyway, to answer your question you don't 'encode' C files, you compile 'm, with a compiler You'll also need an SDK. (Well, unless you want to do it the hard way)
I somehow doubt this'll help you out very much though. Learn some basic stuff about programming and computers first.
OK, let's start from the beginning. If you have a .c file and a .h file you need to compile them first. One way to do this would be to grab a copy of devkitARM off of devkit.tk and a copy of the alternative SDK from www.mirkoroller.de and follow the instructions on setting up devkitARM.