These instructions worked for macOS Sierra. 

1. Pair the device via the Bluetooth preferences. It will show up as Makeblock. After pairing it will show as Not Connected and this is normal. Pairing the device makes it available, but it is not connected to an application.
2. Open mBlock and select the Connect menu followed by selecting the Serial Port submenu.
3. Select the /dev/tty.Makeblock-ELETSPP device.

MakeBlock support forums article:

http://forum.makeblock.com/t/connecting-via-bluetooth-on-os-x/4336