My question involves paternity law for the State of: Washington

My sister was going to marry this guy and he is not not the bio father of her child. When the child was born, they put the non-bio's father's name on the BC. Now, they split and the real father wants his name on the BC. How do we go about taking one off and putting the real fathers name on?

She does not want to get a lawyer if she can do this herself. Can anyone help get me started in the right direction with the right forms?