OpenMCL comes with a Cocoa application called "OpenMCL.app", which provides a graphical IDE for editing, compiling, and running Lisp code. The IDE is a work in progress, and may not yet provide everything you need to be comfortable developing Lisp applications. It is sufficient for developing the CurrencyConverter example application, though, and this HOWTO assumes that you wll use it.
The IDE is distributed in source form with OpenMCL, and you need to build it before you can use it. Fortunately, building the IDE is very easy.
First, make sure you have a recent version of OpenMCL, and that it is installed correctly. You can obtain OpenMCL from Clozure's OpenMCL page. The CVS access page explains how to get more recent development versions, and the documentation page on installation explains how to install it correctly.
Once you have a working OpenMCL, you should be able to open a Terminal window and run the command "openmcl" to obtain a running OpenMCL session:

Now, assuming OpenMCL is installed correctly, you can build the IDE by typing:
(require "COCOA-APPLICATION")
OpenMCL compiles and loads the source files needed to build the IDE, then writes the executable to the path:
ccl/cocoa-ide/OpenMCL.app
OpenMCL then quits (because the implementation of SAVE-APPLICATION, which writes the executable, causes OpenMCL to quit).
You should now be able to start the IDE by double-clicking the application in ccl/cocoa-ide/OpenMCL.app. Please note that this Cocoa application bundle exists in the OpenMCL distribution as it comes from Clozure, but it won't work until you follow these instructions to build the IDE. The bundle as it comes from Clozure is doesn't have the necessary executable in it until you build it.
You should now be ready to continue with the HOWTO, using OpenMCL.app to create and edit Lisp files.