You will need to file a complaint and serve the individual. Depending on what you are suing the person for will determine what court you need to file your complaint in.
It is impossible to answer a question when you provide no factual background. My suggestion is for you to pay an attorney for his time and discuss the facts of your case.
There's not really enough information given to permit an answer to this question. Consult a local personal injury lawyer who can review the details with you and who knows the laws of your state.
Get a lawyer to prepare and file the suit. The problem will be in identifying the person. Since Facebook is in Washington (I believe), you will end up in Federal Court based on Diversity of Citizenship.
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