It's like gen, you can look for the manual on the official site.
Position 0 is for manual winding (after unlocking the crown protector, of course)
Position 1 is for moving only the hour hand, and it's meant to be used to set the local time while travelling
Position 2 is for hour AND minute adjust. The manual says that before setting the correct hour/minute, be sure that the hour hand is exactly over the GMT hand.
Basically, hour and GMT hand normally are aligned (GMT function is 12h as for gen) and you fix your time from position 2. When you travel, you move only the hour hand to match the local time, while the GMT hand will always point to your home time.
There is no quick-date setting... you must move the hour hand 24h for date advance. This can be done both from position 1 and position 2, but from position 1 is a lot quicker.
As always, avoid to set the date between 10PM and 2AM, like every other watch.