"How long after abuse occurs can I ask for charges to be filed?"
*** What was the date of the incident and what happened (can affect SOL)?
"(I have a police report) And how do I go about getting charges filled?"
*** If the police have investigated and found sufficient cause to bring charges they will do so. If for some reason you don't think the police were correct in not bringing charges, you can contact your local DA directly to see if they will take action.