How to add breakpoint in iphone SDK 3.1.2?

Set cursor on the line where you need the breakpoint and in Run menu in Manage breakpoints select Add breakpoint in the current line. Or Cmd+backslash on the keyboard.
I attached the screenshot.

Screen-shot-2010-01-18-at-4.05.1.png

Sorry. Here is the correct screenshot.
Screen-shot-2010-02-02-at-7.07.0.png

Do you know what are the
debug console
mini debugger
editor
under preference -> debug?

Run menu -> Debug
Run menu -> Console
You asked one question and showed the answer. Please do not continue in this thread.

I added a breakpoint in first line insides main, and run it as debug mode.

But, why it did not stop at breakpoint?

I do not see your computer to be sure. I guess, you need to Activate breakpoints.
I attached few screenshots. Please ask new questions in new thread.
Screen-shot-2010-02-03-at-6.27.5.png

Great! breakpoints works now, many thanks

You are welcome