Christmas light strings have to be plugged into an outlet as a source of electricity to power the lights. Some Christmas lights can be bright, but you can dim the lights on your Christmas tree or in other areas of your home by plugging the light string into a dimmer device, which can be purchased at lighting stores, home improvement stores and many department stores. The dimmer plug-in allows you to control the brightness level of your Christmas lights.
Purchase a light dimmer plug-in. Check that the plug-in you are purchasing matches the two-prong or three-prong design of the Christmas lights you will be plugging into the dimmer. Also, check to see how the dimmer works—whether it is a switch or a sliding mechanism that allows you control the brightness of the lights. You should buy a dimming plug-in device for each of the light strings you want to dim.
Plug the dimming device into the electric outlet near the area of the Christmas lights.
Plug the Christmas lights into the dimmer device.
Move the dimmer switch to change the brightness level of the Christmas lights. Switch or slide the control to adjust the brightness of the Christmas lights that are plugged into the device.