This External White Plug-In Dimmer Switch doesn't need to be installed.
All you need is to plug it on a standard Type I power socket; plug your LED lamp onto the dimmer's own socket; and turn the rotary knob to adjust the light's brightness.
Think of it as a short single-socket extension cord-with a dimmer.
This is especially handy if you want to use a dimmer to set the ambience of your dimmable LED bulbs or incandescent festoon string but you can use it for your dimmable LED table lamp or floor lamp as well.
The External Dimmer comes with a 2m white power lead.