Clutch pedal went to the floor

1993 BMW 528e Manual 5-speed mileage: 141,000. Overnight, my clutch pedal went to the floor. The car has a clutch master and the clutch slave appears to be on the outside of the transmission housing down below. The fluid is within recommended levels. I had a clutch replacement about 18 months ago and had problems with it needing occasional bleeding, but these problems were infrequent and seemed minor. This time, I believe bleeding the line is again the place to start, but I was not the guy who originally did the work. My problem is I can't find a valve or release for the air anywhere near the slave. The slave has a little nub/nozzle at the bottom, but nothing is attached to it and my long-time trusted mechanic says this is not involved. I'm trying to avoid a tow. How do I bleed the line exactly?