Measuring electrical power of light bulbs can be done in different ways to find the amount of power a device uses. Most store bought appliances have a label indicating the amount of power that particular device uses. To get a more accurate value, two of three things must be known. They are the voltage across the device, the current used by the device and the resistance of the device. Power is equal to voltage times current; voltage squared divided by the resistance; and current squared times the resistance.
Write down the reading and unplug the light bulb holder. Change the setting on the multimeter to read current. This is usually the 10A setting. On some meters , one of the probes has to be moved to a different slot on the meter.
Take the readings and multiply them together. Using the examples would mean 115 volts times 1.5 amps equals 172.5 watts. Watts is a unit of power.