In a majority of the states you will need to get this information from the police.

It is the law enforcement's responsibility to include this information on the accident report. If there is no accident report, then you should contact law enforcement to file a report. If you have a report, you will need to contact the police authority that wrote up the report.

You can contact your insurance company and they can assist you in this matter.

If you cannot locate the responsible party, then you will have to file the claim under your policy (if you have coverage that will cover the claim).