If the question is how you go about pressing charges, you would need to inform the police of the facts and your intention to press charges. They will then work with the state attorney to decide whether, in fact, there will be a criminal prosecution. You do NOT get to decide whether there is a criminal prosecution, but your stated intent to press charges may have influence on whether the state attorney has an interest in prosecuting.
You also may be able to sue for damages incurred, if any, due to the assault, battery, infliction of emotional distress, etc.
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Unlike civil litigation, in criminal litigation lawsuits are not filed by individuals. You can, as the attorney above stated, speak with the police and later work with the state attorney on any charges they decide to bring. However, what the state attorney decides is legally justified is what will might be charged with. He may also only be charged with offenses that the State Attorney believes he can prove. And by the end of the case, some of the charges may be dropped that you may feel are still justified. It may even be part of a plea bargain that the state attorney suggests.
I understand that you are both frightened and angry at what he has done. I understand that you want him to be punished for his transgressions. And if the state attorney files the case, he may be. But in the calculus of criminal law, the results are much less about vindicating a victim's sense of injustice than about legal matters: What he did, what the police did in collecting evidence, and what can be proven beyond a reasonable doubt.
So, if you feel he has harmed you and broken the law, feel free to go to the police and press charges. But do not expect that the state attorney's job is dependent upon satisfying your sense of justice. Your personal feelings as the victim are not what will rule the day in sentencing. Your personal feelings may assist with the state attorney's job, but ultimately, what happens is is in the hands of the state attorney, the defense attorney, the judge and the jury.
This posting is for informational purposes only. Answering this question does not constitute forming a lawyer/client relationship. For more complete advice, specialized to your situation and locality, consult a lawyer from that state.