The next two steps show how to safely measure larger electrolytic capacitors. These capacitors look like small cylinders. The iFixit multimeter can only measure capacitance up to ~100mF (millifarads).

Plug the black lead into the COM port. Plug the red lead into the right port.

Power down the circuit you're measuring, if you're measuring the capacitor while it's still connected to the circuit.

Make sure the capacitor is sufficiently discharged:

Turn the function dial to the DC volt mode.

Carefully touch the probes to the capacitor's leads/pads to measure voltage. Treat the circuit as a live circuit and be careful not to touch anything else with your probes.

Make sure the capacitor voltage is 10V or less. If it isn't, wait a minute to let the capacitor self-discharge, or use a capacitor discharge tool to discharge the capacitor.

As you measure the capacitor's voltage, the multimeter may slowly charge the capacitor up. Don't measure the capacitor for too long to prevent this from happening.