Hi Gegatso & welcome to the forums :)
I haven't reviewed the Logic 101 tutorial since your question, but I'm pretty sure Martin shows how to add AUX Channels (or any channel strip, e.g. Output 1-2) from the Mixer to the Arrange area. Once a channel is in the Arrange area ( as a track) then you can easily draw in automation.
In the Mixer, Control/Right-click on the Channel strip (e.g. Output 1-2) and choose:
'Create/Select Arrange Track'.
By the way, if you want to add volume automation to the Output 1-2 in real-time without adding it to the Arrange area, you can choose latch/touch mode on the Channel Strip in the Mixer and move the volume fader during playback.