Disconnect the resistor from any circuitry. If a resistor is wired parallel to other circuits, the electricity produced by the multimeter will have multiple paths available to it, making the resistance read much lower than it really is.
Set your multimeter to resistance by turning the dial to the omega symbol. Turn the power on.
Hold one test lead in each hand so that your fingers are touching only the handles and not the metal probes. Touch one lead to each wire coming out of the resistor. It doesn't matter which lead touches which wire.
Read the resistance value from the multimeter screen. If you are using a digital multimeter, read the value directly off the display screen. If you are using an analog multimeter, a needle swings to the value on a dial.