Insurance companies and state laws differ but generally speaking the motorist who collided with your parked car will be responsible for your damages. Hopefully the police report was called to the scene and filed a police report. If so the police report might help to assign blame and thus help you when filing your claim with the at-fault's insurance company.

It is likely that the insurance company of the person who hit your vehicle will do their own investigation into the incident. There is always a possibility that the insurance company could decide that the person was not to blame and deny a claim. If there is plenty of proof that the person is at-fault then this typically will not occur.

If you have collision coverage you could put this incident through your insurance company, which would make you pay the associated deductible. You then might decide to go after the at-fault party to be reimbursed for the deductible amount.

Start with getting the at-fault party's insurance information and contact them to make a claim. Seven Steps to Filing Your Car Insurance Claim is an article that can be helpful.