Bobbin won't thread

Sounds like the bottom tension is to slack.
Look at the side of your bobbin case, when you thread the bobbin thread part of the route it runs is under a flat leaf spring. There is usually 2 very small scews on this leaf spring one screw holds the spring onto the casing and will be tight. The other is the tension adjuster screw, turn this screw clockwise half a turn at a time. After each half turn pull the bobbin thread until slight resistance is felt. Then try sewing if bunching/tangles still occur more tension is required, this is trial and error until the tension is corrert.
If you want a new manual try this website if your machine is not listed email them and they will try to help.
www.sewusa.com