Adding an external executable in Xcode 4

I would like to debug Firefox code on OS X. I'm reading from this page and it tells me:

Now you need to add the executable. Select Project > New Custom Executable and type a pretty name, then click the Choose button to locate the .app file that you want to debug (Mozilla.app, Firefox.app, DeerPar开发者_StackOverflow中文版kDebug.app etc). The .app file is

But with xcode 4 there is no Projects menu. I can't seem to find out how to add a custom executable. I have successfully built Firefox but I just can't debug it because I don't know how to add an executable in Xcode 4. I suspect the steps in the link were for Xcode 3.

Under Xcode 4 you will have to edit a scheme to run an executable. Select a scheme (or duplicate one for your target) then select the "Run" phase. You will see an "Executable" pop-up menu, select which executable you wish to use then run your target. There are other settings for specifying the arguments, etc just as in Xcode 3.