see the manual(gamestudio sdk part),
setup your ide(preferably vc++ 2008 express), add lib and include dir(gstudio7/sdk_plugin) and compile it.
i can provide you a little example i started(but have no time to contunie) that uses sqlite3 amalgamation(or something like that), and lets you use opendb and exec commands(yea, really works) in lite-c. If you are experienced in c++ this will get you started i think.
(ps. you can write wrappers for dlls to use them with lite-c. like load the dll in litec and write another one with DLLFUNC s inside to use that external dll.)