Here is a step-by-step picture tutorial on threading your bobbin.
Step 1: Hold your bobbin so that the thread is coming off of the bobbin in a counter clockwise motion:
Step 2: Insert the bobbin into the bobbin case, ensuring the thread is coming off of the bobbin in a counter clockwise motion:
Step 3: Pull the thread into the notch of the bobbin case:
Step 4: Find the "hook" and pull the thread so the hook catches it:
Step 5: Pull the thread to the right of the "pig tail" and wrap the thread in a clockwise motion around the "pig tail" twice; be sure to pull thread out a length of about two inches:
Step 6: Insert bobbin case into bobbin area as seen. You will know the bobbin case is in position when you hear a "click":
Step 7: With the needle threaded, raised to its up-most position and the presser foot up, hold the top thread with your left hand while turning the hand wheel towards you. The top thread will catch the bottom thread and bring it through the needle plate:
Step 8: Using the small screwdriver that came with your machine or other device, slide it beneath the presser foot to catch the threads and pull them out:
The lower portion of your machine is now threaded!