Linking Multiple .C Modules and malloc()

I've been writing a program recently, and I found that it got too big to manage all in one .C file.  However I've run into a problem trying to link all of the files together.  I'm using Turbo C, and defined all of the .C files as part of a project.  But when I tried to link the program, (using the "Make" option) I got tons of "Undefined symbol '...' in function ..." errors.  I've got all my #include files defined in the main module (the one with the main() function), and I don't think the rest of the modules are seeing them.  But when I put the include files in all of the modules, I get "Duplicate symbol ..." (or something like that) errors.  How do I get the linker to recognise the include files for all of the modules?

Also, how would I go about allocating memory for a 250 element array of structures?  I tried:

  soldier = malloc(sizeof(soldier) * 250));

where 'soldier' was defined as:

  struct soldier *soldier;

I've probably made some pointer mistake, but I'm new to C and I'm still a little puzzled with all the different pointer operators (*, &, etc.).  Any help would be GREATLY appreciated as I can't go any farther with my program without clearing these problems up.  Thanks...