How is a reed switch used to charge/discharge a capacitor?
To charge the capacitor, a normally open reed switch is interposed between a voltage source and the capacitor, then the reed switch is exposed to a magnetic field of sufficient intensity that it causes the contacts to attract each other until they touch, allowing charge to flow from the voltage source, through the made contacts, and into the capacitor. 

Once the capacitor is charged, the magnetic field can be removed, allowing the contacts to open and the charge in the capacitor to remain there.

In order to discharge the capacitor, the voltage source is removed and replaced with a load of some kind, the reed switch energized once again by the magnetic field and, when the contacts make, the charge stored in the capacitor will flow into the load, discharging the capacitor.