To file a lawsuit against someone in California, there are three things to do first:
You need to inform the organization you work in, whether it is your superior, human resources, or someone responsible, to hear and register employees' complaints and take action.
If you continue to face sexual harassment, the next step is to file a complaint with the California Department of Fair Employment and Housing (DFEH). If you need to file a lawsuit, this step is necessary since, without the right to sue letter given to the employee, they cannot file a valid lawsuit.
After obtaining the right to sue the letter, you will have one year to file a valid sexual harassment lawsuit.