XCode 4 "add build setting condition" not enabled

I am trying to include Layar Player in the iPhone application I am developing in XC开发者_如何学运维ode 4. One of the steps of section "1.3.1.2 Universal build configuration" asks to click on "Add Build Setting Condition".

But that option is not enabled (it is shown in grey). Only the "Add User-defined Setting" is enabled. How can I make this option to be enabled or what could be wrong?

To enable the Add Build Setting Condition menu item in Xcode 4, you must select a specific build configuration for a build setting. Click the disclosure triangle next to the build setting to see the build configurations, which should be Debug and Release. When you move the cursor over a build configuration or select the configuration, a small + button should appear next the name of the build configuration. Click the + button to add a conditional build setting.