My soon to be husband has been there for my son since Ive separated and divorced my ex husband who is in and out of mine and my sons life constently. My ex is in somewhere in California and I have no direct way to contact him. My soon to be wants to adopt him after we get married. How does this work and where do I start?

Hire an attorney, he will attempt to find your ex and get him to sign permission to adopt. Then he will take that and file adoption paper work with the court.