1. Fix the hydraulic leak
2. Top off the reservior.
3. Person #1: Mash the clutch pedal to the floor and hold it.
4. get person # 2 to crack open the bleeder valve on the slave to release the pressure.
5. Tighten the bleeder valve.
6. Release the clutch pedal.
7. Repeat steps 2-6 until fluid runs clear, pedal feels good, and no more air comes out.

If you wind up replacing the master cylinder, bench bleed it. There will be instructions for this included with your part.