For a complete example demonstrating how to build a standalone Cocoa application which uses a nib file, see
examples/objc/area-calculator/area-calculator.lisp
and
examples/objc/area-calculator/deliver.lisp
.
The area calculator example connects the nib file generated by Apple's Interface Builder to a Lisp implementation of an Objective-C class which acts as the MVC controller.
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 15 Dec 2011