Lets do this step by step
Take A12 off of camera
Open A12, put spool and film in their proper location, loop film around, make sure it goes under the little clamp that's operated by the insert release key, thread film, turn knurled knob til the arrows line line, put into back and lock it. Crank the knob on the A12 til it stops, fold it back AND LEAVE IT ALONE
Make sure camera is cocked, put back on, remove darkslide, shoot, wind camera
Repeat til the knob on the camera locks up (after frame 12)
UNFOLD crank on A12, crank til you feel film come off the spool and voila...