Shakespear,
It is not actually a "bulb", but I am assuming you have located the device since you are evidently empting some of your urine. It is a somewhat flat device which can be pressed on one end. The other end is connected to a tube going to the cuff surrounding the urethra. To completly drain, press the device two or three times, trying to flatten the thing between your thumb and forefinger, or which ever fingers work the best.
Why do you think you are not empting completely? Maybe you should call the doctor's office and/or schedule a visit if you are not empting completely.
Gene214