How do I measure current with this multimeter?

For AC or DC current, turn the Range Selector Switch to the 20A position (or 20A~ for AC), starting with the highest range if amperage is unknown. Plug the red lead into the 20A Jack (or mA Jack for currents under 200mA) and the black lead into the COM Jack. Note that amperage is always tested in series with the circuit. If the reading is less than 0.2 amps, switch the red lead to the VΩmA Jack and set the selector to 200 mA.