The arrowhead side of the lock needs to face the right, the flat end of the spring (the opposite end to the open bit) goes on opposite side to the arrowhead (there should be a mark on the orginal lock to illustrate where abouts it was). The loops at the top face inwards - towards the handle - and the rod goes through the two loops of the spring, the door handle and the lock itself. When assembling the door back together, hold the lock in the closed position, ensuring that the spring is in place to keep it there. I hope that helps.
joanwilder, September 2008