The location for the lights and power source may vary but regardless of this the connections to the switches will always be the same. When you ask how its very vague there are quite a few steps to pulling wire installing box es and wiring traveler wires.

How To Add An Electrical Outlet From A Light Switch
Add 3 way switch to existing light. This night light replaces any existing single pole or 3 way switch devices and offers a hidden sensor that automatically controls the night light plus five adjustable light levels including off. How to wire a three way switch to a existing single pole light switch circuit. I am not sure if thats easier for you. This is about a 15 min project plus the time it takes to chase the wire took me about 30 minutes to chase the wire. Radiant screwless wall plate not included. In this video i explain how to install a three switch from your existing one way one switch.
If i can do it so can you. Once youre done youll be able to control a light from two switches. Connect the hot wire from the source to the common terminal on one 3 way and the hot wire from the lights to the common on the other 3 way. Yet here i am adding a switch to an existing light. Dominick amorosso decemberj2012 110 volt electrical 11 comments 24039 views in this video i explain just how easy it is to add a three way switch to an existing single pole one switch lighting circuit. Wiring a 3 way light switch is certainly more.
For detailed night light information visit our night lights page. You will need to pull new 123 cable from the switch you have described to the new 3 way switch you are adding. This story features diagrams that show how to wire 3 way switches. To control lights from 2 locations you need two 3 way switches. Then of course youll have to swap your existing switch for a 3 way switch. If you could pull a 3 wire to replace the 2 wire between the source power light fixture and the 3 way switch box on the right than you could then feed a light fixture off that 3 way.
Wiring three way switches jeff when adding additional lighting to an existing three way switch configuration the only place the additional lights may be wired to are at the existing light fixture or to the switch box where the existing light fixture is wired to. The wiring is more complicated than a traditional single pole switch but well explain how to make the connections.