Welcome TomJones:
The best diagram of a 3-way switch is on the package and, sometimes, even on the switches themselves. Most folks have trouble with the wire called a "common"; in this case the wire is common to the two switches, is usually red and goes on a screw marked "common". That wire is not connected to anything else; it is simply a traveler between the two switches, getting that right is the biggest hurdle and the rest is a breeze.
Glenn