Sewing machines have a bobbin in their bases which holds thread. The thread in the bobbin holds the upper thread in the material when the sewing machine pulls it through the opening in the foot. The bobbin in the base is very important to the process. If the bobbin's thread is not correctly put into the machine, the stitch will not hold. Usually the bobbin is placed inside the machine on the side, however, with certain Singer sewing machines the bobbin is a top loading bobbin.
Raise the presser foot.
Turn the wheel manually until the needle is at the highest position.
Pull out the plate and remove the empty bobbin from the shuttle.
Pull 2 inches of thread from the bobbin then place the bobbin into the shuttle.
Hold the bobbin with one finger and pull the thread through the catch in the shuttle.
Pull the thread toward the back of the machine until about 4 inches are drawn.
Hold the thread with one hand and close the plate.
If the machine allows rethreading at the top, use it. It is a good way to not only reuse the same bobbin but to make sure the bobbin is correctly threaded.
Keep your foot off the controller, as a slight movement could make the needle move and injure your hand.