If your employee has a temporary national register number (INSS), you can easily modify it once the definitive INSS is communicated.
1. Go to "My company" > "My staff", filter on the INSS of the employee for whom you want to make the change
2. Click on the icon "Actions", then on "Modify" in the employee file
3. Fill in the final INSS and click on "Seach"
The INSS filled in will become the new reference for the employee