Plus learn how to change a single pole switch to a 3 way switch. To replace an ordinary one way onoff switch with a dimmer is easy.

Ceiling Fan Switch Wiring Electrical 101
One way dimmer switch wiring. This allows you to turn the light on and off from one spot in the house. This fixture has no on and off label and has three terminals behind the switch. With a three way dimmer you can control a light with two switches. Obviously the reverse is true to dim and turn off. With a standard single pole dimmer a single switch controls the light. Attach to the bonded ground wires in the switch box.
In most cases the two switch wires will be some color other than green or white usually black. But one of the wires may be white if your house is wired with plastic sheathed cable. If only one switch controls the light purchase a single pole dimmer. This enerlites dimmer can be used as a single pole or 3 way dimmer switch. Dont need to change wiring just switch and dimmable light bulbs or down lights. You will need a three way dimmer and a three way switch.
3 way dimmer switches typically come with the following pre wired leads. This lets you dim from one location and turn the lights on and off from another. When you control a light in two separate switches you actually have a three way switch. A basic light switch is a single pole with an on and off label. The most basic and consequently the least expensive variety of switch is the simple dial that you turn to click on and turn further to make the light brighter. Replacing standard light switch with dimmer one is quite easy.
In this video im showing how to do this. Put a wrap of black tape around the white conductor to label it as a hot wire. I show how to install a single pole dimmer switch. Wiring a standard 3 way dimmer switch. These wires attach to the travelers which are the pair of wires attached to the two screws at one end of the regular 3 way switch.