Position the qt wallet near the middle of your screen.
Take a house key (car key may be too big)
Push your key into the lock icon near the bottom right of the wallet, may take significant pressure.
Once it's all the way in turn it 90 degrees to the left to unlock, to the right to relock.

HTH, feel free to tip  

edit: sry, thought you were joking.  Johnny crypto posted the help below.