Creating a Project
A project to create a Cocoa application in Lisp includes at least a file of Lisp code and a nibfile--a file of user-interface objects created by Apple's InterfaceBuilder application. We'll begin by creating those files and a place to store them.
This HOWTO includes a working nibfile ("CurrencyConverter.nib") and a Lisp source file ("CurrencyConverter.lisp"). You can build a working copy of the example application by using these files, but you probably shouldn't. If you want to understand how to build your own Lisp application projects, you should follow the instructions here to create your own source file and nibfile, and use the example files only for reference in case something goes wrong.
Create the Project Folder
First, create a project folder to hold the files you are going to create. When your project is complete, the folder will contain a nibfile that defines the user interface, and a Lisp source file that defines the behavior of the application. Those two files are really all there is to a Lisp application, though not all applications are as simple as this currency converter. For more complex applications it makes sense to split your UI into several nibfiles, and to split your implementation into several source files. The basic principle remains the same, however: nibfiles define your user interface, and Lisp files define your application's behavior.
Create a folder somewhere convenient, and name it "currency-converter". Next we will use Apple's InterfaceBuilder application to create the user interface. The next page tells you how to do that; when you create your nibfile, save it into your "currency-converter" folder.