How to enter developer mode?

When running Xcode 4.3 for the first time, it asked me if I'd wanted to enter developer mode. Entering developer mode lets me do things like debug your project without Xcode asking me for my user account’s password. At the time it asked me, I said no. I want to enter my mac into developer mode now, but can't find a setting in preferences whatsoever. How may I enter developer mode?