The door which was closed opens as you pull off the white tab and the black tab comes out.
Do not pull the white tab when you see the black tab out.
Hold the black tab with fingers and pull it off straight from the camera for about 2 sec,
which makes developing begin.
Hang it or put it on a flat place carefully and don't either touch or bend it between developing.
In case you are outside, be careful not to have it blown by the wind.
Follow the manual as to the developing time.