As a PreK teacher, I would want to make sure that my students understand how important it is to stay on the websites that I pull up for them, as well as never giving out personal information or talking to strange people online.
One resource that Ed Tech has for me to use is BrainPop. On BrainPop, there is a video called "Online Safety". I would start out with students watching this video. Then I would lead a discussion about how important it is to follow the rules of the internet (not talking to strangers, not typing your real name, and staying on the sites that the teacher pulls up). I would also probably make up a song that we would practice that reinforces these rules. We would then practice what following these rules looks like.
During open house or another organized event, I would talk to parents about the importance of internet safety and monitoring their children while online. I would teach them the song that the students learned and we would discuss other things like putting the computer in a family room, where computer usage can be easily monitored.