The contested final hearing is a formal court hearing (like the interim hearing, if you had one). The Judge (or Magistrate where child support is the only issue) listens to both sides, then issues a final order. You may give your own testimony and present witnesses and documents. You may cross-examine the other party. The court rules of evidence and procedure apply.
The Magistrate (or Judge) may tell you on the day of the hearing what the final order will say. Or you may receive it in the mail after it has been drafted and signed. The Order takes effect when the clerk enters it on the "court docket," usually the same day the Judge or Magistrate signs it.