What would my husband of almost three years have to do to adopt my ten year old?

My son was born in 2005 it felt like I always had to force his dad to even want to see him so when I quit pushing for him to visit or me visit him then he started to act more distant. We had a relationship until my son was almost three which was the last time he seen our son. I would try to call and if he answered he was drunk (which is irrelevant ) but I didn't want my son that was almost three hear something like that. Other than that I tried finding him on social media to see he's blocked me. He hasn't contacted me or my son since he was almost three and since then I have been in a relationship with a man I married January 3, 2013. My husband has known my son since he was 18 months old and wants nothing more than to adopt. Is there a way he can do that and if so how do we do it?