[iOS] Link new xib to File's Owner

The correct answer was given by user763308:

To link a .xib to a class under Xcode4:

1. Open your .xib.
2. In placeholder: select File's Owner.
3. In the third thumbnail:"Identity Inspector" of the right panel, edit the "Custom Class" field and enter the name of your class.

I also then had to:

1. Click the root view under Objects.
2. Click the last tab: "Show Connections".
3. Drag "New referencing outlet" to "File's Owner" and select "view".

Reference