Hello Sally,
First of all check the tension on the bobbin and make sure it is in the correct way round, you should be able to pull the thread through with some resistence, if it is too loose toghten the screw on the bobbin case about a quarter of a turn at a time until you get it right, you can adjust the top tension if you have to by pushing the numbered dial in so it is away from the chrome thumb nut and then turn the nut either way so you get the pin into a different hole but try the bottom tension first, email me below if you have any problems.
ken
drivewithken@blueyonder.co.uk
February 2009