I'll try to update the wiki on it, in the mean time, all element properties what aren't dynamic (don't sit in "if" statements) go in powder.h, anything else goes in powder.c and possibly in some other files.
I sort of know how to code... Any way you are trying to code a *.c file so after your done coding you must compile it. I still don't any compiler yet... for more info about powder toy coding you can visit powdertoy's wiki! hope it help