You must file a Summons and Complaint for Separation as you would for Divorce and have it personnally served by a process server on the othet party. The other party then has 20 -30 days to reply with an Answer.
The procedural and legal requirements require the advice of experienced counsel and should not be left to self help. These matter are too important to do by yourself.
If you are living in the NYC metro area , please call me at 212-370-1660 to discuss
mediating you Separation. I can help.
Leonard M. Weiner, Esq./Divorce Solutions