Adding text to a window.

You need to use a label NOT a TextField. You can find the label in the Object Library in Interface Builder (or the integrated Xcode 4 editor ) by searching for 'label.' The user will not be able to edit a label. You can also change the state of a text field by unchecking the enabled check box in the IB Inspector.
You could also do it like this in code, provided you have an IBOutlet connected to the NSTextField

Code:

[myTextField setEnabled:NO];

NOTE:
Labels and TextFields are all NSTextFields, the label is usually not changed by the user.

 

In IB there should be a Label object you can drag over. It's really just an NSTextField, but configured to be non-editable, non-selectable and no border.