Because you work with children (and others who work with children) daily, you are able to notice behavior changes, not only in the students you work with, but in the adults in your life: Other teachers, parents, school or program staff, and older children not under your direct supervision. This ability to notice changes puts you in a special position to stop child sexual abuse... before it can happen, as well as intervening and reporting where it is suspected.
Knowing the warning behaviors in potential abusers is a great step in being able have conversations with adults or older children who may be at-risk for sexually abusing a child.
Knowing how to help children who show concerning sexual behavior is a plus. Pretending it did not happen and hoping it goes away may solve the problem, but it may also enable more inappropriate behavior. Know when to get help.
Victims of sexual abuse, and those at-risk for child sexual abuse, need very different approaches. A victim will need to process at their own pace, where a potential abuser may need the extra attention of you checking in more on how they are feeling to show that you care. Responding to anyone is always a balancing act: With victims, you will want to let them set the pace, and with potential abusers, you will want to take more initiative.
Knowing what behaviors are appropriate in the children you work with, and which behaviors are not, is a great way of being able to tell when a child may have been sexually abused. Knowing how to make safety plans and react to certain situations is also a good idea.
Knowing how to report child sexual abuse, or other kinds of abuse, can be as simple as contacting a child advocacy center in your area. Of course, you can also contact the police or child protective services. It may help to write down the information you need to report beforehand.
Knowing the facts about child sexual abuse is a great way of preventing child sexual abuse, because you are aware of who perpetrates abuse and which situations are common factors in abuse.
There are many resources out there for you to use. One company I am aware of is this one, which also offers a downloadable/printable poster that could be used in classrooms. There is also a handy resource page available at The Mama Bear Effect. Darkness to Light also has a program called Stewards of Children that can provide people with an overview of the topic of child sexual abuse and prevention steps, though it can cost money and not all of their facts and terminology are accurate.