I just found out that my daughter's biological father killed himself. I am getting married and what my future husband to adopt my daughter. How can I get this done?

You can get is done through step-parent adoption.Some states have restrictions on that matter. You should have been married for at least a year before you file for adoption.
Another thing in your case is that it is possible the grandparents to be awarded with visitation.

What you need most is documentation. Also was your ex declared the legal father by the courts ?

Get a copy of his death certificate. With that, you should have no problem getting the adoption when you meet the requirements.

.... You should have been married for at least a year before you file for adoption. ...

Again, depending on the state. I was able to file a step-father adoption petition a week after I married my daughter's mother.