How to Wind a Bobbin
The bobbin is the small circular thread-holder that holds the bottom thread in your sewing machine. This thread is very important because it works together with the top thread to actually create a stitch and hold your fabrics together.
Some bobbins are metal, and some are plastic. Also, some come in different sizes. It is important to make sure that you are using the correct type and size of bobbin that was made for your machine. You can find out which type you should be using from your machine's owner's manual or by doing a Google search that includes the make and model of your sewing machine.
If the automatic bobbin winder that came on your machine is broken, there is no need to fret. There are stand-alone bobbin winders available on the market, such as this one.