The above was for my 320, which is the typical scenario for most cameras and backs.
For my 190, it's slightly different. I only used 1 bobby pin on the spring closer to bottom of camera. The other side of the spring tucks neatly under the "thin box" next to it (lower part of below photo) and a pin is not necessary. The "thin box" houses the electronic timer which I don't use coz I won't bother using batteries on my 190.