There are 2 diagrams below, the first one is a diagram of how to wire 3 switches to the same light.  You use a combination of two 3-way switches with a 4-way switch in between. 
The second diagram shows how to wire 4 switches to the same light by adding another 4-way switch in series.
You can [...]

This is a typical diagram of how to connect 2 switches to the same light. It’s especially handy for stairs, hallways, and big rooms.
You will notice that the power feed goes into one switch box, while the switch leg (light wire) goes into the other.  There is also a “traveler” line that connects the two together.
Traveler:
The [...]