Arduino Dock Initial Setup tutorial is related to Omega (ie the previous version) and the first version of the Arduino Dock.
Use it carefully!
I wired up the Expansion board with Omega2+ and the Arduino Dock 2 expansion - BUT I could NOT get the Omega2+ to power up at all.
Omega2 is a 3.3V povered device and its GPIO pins are not 5V tolerant.
VIH (Voltage Input High) absolute maximum is 3.3V - 10% + 0.3V = 3.27V ... 3.3V + 10% + 0.3V = 3.93V.
Arduino is 5V powered on the Arduino Dock 2 so it may damage your Omega2 if you connect them in the mentioned way.