This is the lead that you previously identified with the minus symbol on the side of the capacitor.

The quickest way to discharge a capacitor is to touch the two terminals of the capacitor together, as is shown below. Use a resistor to discharge the capacitor leads.

You can use either a 1.8 k or a 2.2 kilo ohm 5 to 10 watt resistor to discharge the high voltage capacitor … To discharge a capacitor, the two leads of the capacitor must be connected together so that there is a path for the current to drain through so the capacitor becomes depleted of its power.

Touch the black, or negative, tip of the discharge pen to the capacitor's cathode. Touch the red, or positive, tip of the discharge pen to the other lead, the capacitor's anode. Place the screwdriver's metal end across the two terminals that protrude from the capacitor. Again, this is the quickest way to discharge a capacitor.

Third method and also my favorite method is to place the leads of a high wattage resistor on the leads of the capacitors you want to discharge.