You’d need to go to court to do it, and if the father has not had his parental rights terminated you’d also need to seek the father’s consent. If he won’t give consent then you still must notify the other parent of the petition for the name change so that he has a chance to oppose the petition. If the child is at least age 14 then the child’s consent may also be needed. You can get more information here: NY name change for minors

