Once an interface has been created, the object code defining those functions (and indeed any variables) must be made available to LispWorks.
In Unix, LispWorks defines the function link-load:read-foreign-modules that either load object files (usually suffixed with " .o ") directly into the Lisp image, extract any required object files from the available archive libraries (usually suffixed with " .a "), or load in shared libraries (usually suffixed with " .so "). The read-foreign-modules function takes a list of module names as its argument.
In Windows the function register-module is the LispWorks interface to Dynamic Link Load (DLL) files. It is used to specify which DLLs are looked up when searching for foreign symbols. For example,
(fli:register-module "MYDLL") registers a connection to the DLL " MYDLL.DLL ".