Add/Edit Voice Actor Role

The popup after pressing the ‘Voice Actor’ button will let you search for the staff member you want to link to the character, which you can then select and confirm.
The language is set on the staff page itself, so if you are adding voice actors for multiple languages, you will need to add the same character again, then add each additional voice actor to the respective duplicate. Example: Tonari no Totoro
Adding a voice actor for Saeba Ryo to the 'City Hunter' anime