Like all libraries, the layers library must be opened before it may be
used.  Check the Layers Autodocs to determine what version of the library
is required for any particular Layers function.

    struct Library *LayersBase;

    if (NULL != (LayersBase = OpenLibrary("layers.library",33L)))
        {
        /* use Layers library */

        CloseLibrary((struct Library *)LayersBase);
        }