Summarize:

Turn the balance wheel at the right side of the machine, doing so until the needle reaches its highest position.  Note that the machine should be turned off at this point to minimize the risk of injury or damage. Only turn the balance wheel toward you, moving it counterclockwise. Do not turn it away from you. If necessary, raise the presser foot lever at this time, as well. Open the shuttle cover and lift the bobbin case out of the machine by pulling on the bobbin case latch.  The shuttle cover should be located behind the extension table and on the front of the machine. Pull the bobbin case latch toward you. You should feel the case loosen from within the machine. Continue pulling the latch toward you to remove the case from the machine completely. Slide the bobbin into the bobbin case and slip the bobbin thread tail through the slot in the case.  Unwind roughly 4 inches (10 cm) of thread before placing the bobbin in its case. This is the tail of thread you'll need to work with in this step. Hold the bobbin case so that the hook of the latch rests on your thumb. Hold the bobbin so that thread appears to wrap around in a clockwise rotation. Slip the bobbin into its case with the tail of thread hanging out. Pull the tail of thread into the natural groove of the case, sliding it until it fits under the spring clip and through the thread guide hole (delivery eye) of the case. Hold the bobbin case by its latch again, then insert it back into the machine. Release the latch after the bobbin case locks in place.  The latch of the case should fit into the notch at the top of the shuttle race inside the machine. If loaded properly, the case should not be able to move around inside the machine. Turn the balance wheel at the right side of the machine, moving it toward you (a counterclockwise rotation). The needle must sink into the base of the machine and rise back up to its highest position again.  Firmly hold the end of the upper needle thread with your left hand while turning the balance wheel with your right, applying a light amount of tension to that thread in the process. Do not turn the balance wheel away from you (a clockwise rotation). If done correctly, the upper thread should catch the lower thread during this process, bringing the lower thread out from the base of the machine in a large loop. Use your finger to carefully catch the loop of thread you just pulled up, breaking open the loop in the process. You should see two separate tails of thread: one extending from the needle (the upper thread) and one extending out from the base of the machine (the lower thread). Pull on both threads separately until you have a 6-inch (15-cm) tail of each. Position both tails so that they extend out toward the back of the machine.  Both threads should fall straight behind the presser foot. The upper thread should pass in between the toes of the presser foot. Read through the steps again and check the way that both the top and bottom threads have been prepared. If everything was done correctly, the machine is now threaded and should be ready to use.
Raise the needle. Remove the bobbin case. Insert the bobbin into its case. Return the case to the machine. Cycle the needle once. Catch the loop. Straighten out both threads. Double check.