setting. The crown is used to set the time and the pusher is used to set all other functions (which are synchronized). There are only 2 caveats:
1. When the window under the "12" and the months subdial is red (as in the below photo), just leave the setting alone (do not move hands backwards as date change gears are engaged). It is OK to move the hands clockwise until the red disappears and then set the date mechanism.
2. If one moves the time too far in advance of the current date/time, it is easier to just let the time "catch up" rather than attempting to go backwards.

Photo from last leap year time change...
You are quite fortunate to have acquired this perpetual. It is an ideal size (in my view) and its slimness is especially appealing.
Enjoy wearing it!
tempusfugit