All you need to do is have him served via a licensed process server. Then the burden will be on him to either answer the summons or you can proceed on his default. Schedule a consult with a Bronx Divorce attorney for a full assessment.
The length of your separation has nothing to do with your divorce unless you are using abandonment as grounds. New York enacted no fault divorce effective October 13, 2010. There is not requirement that your husband sign papers for you to get divorced. However, as stated by another poster, if he is not willing to sign a document acknowledging service, he would have to be served with the summons with notice or summons and complaint.
You should contact an experienced divorce attorney to assist you.