Hello Ursula,
Things you must know about the 449, you must use a good mercerised thread only and no thicker that a number 50 or 40, drop the bobbin in so it turns anti clockwise, the thread goes in a slot on the bobbin case, pull it through the slot and pull the thread to the back, make sure the top tension is about 4 or 5, thread the machine with the presser foot up.
Ken
drivewithken, July 2009