How do I get the Mindstorm EV3 software to recognize an NXT brick via Bluetooth?
Communicating with the NXT from the LEGO MINDSTORMS EV3 software is not supported.
From http://www.lego.com/en-us/mindstorms/support/faq/:

3.10 Is the LEGO® MINDSTORMS® EV3 Home Edition Software backward-compatible with NXT Hardware?
Yes. You can program your NXT Intelligent Brick using the new LEGO MINDSTORMS EV3 Home Edition Software. However, not all Software features are supported by the NXT Intelligent Brick.

It does not explicitly mention Bluetooth, but it is one of features that is not supported.
References:

Compatibility EV3 software with NXT brick - known limits?
http://robotsquare.com/2013/07/16/ev3-nxt-compatibility/