The staff page will let you manage the people that were involved in creating the work. Adding existing staff, creating new staff, and assigning their roles are all done here.
Staff addition panel for the 'City Hunter' anime
The popup after pressing the ‘Add Staff’ button will let you search for the staff member you want to link, which you can then select and confirm. Back on the main page, you’ll now be able to add a role.
Multiple staff can be selected at once. You are also able to search for a new name and continue selecting characters. Everything will be carried over when 'Done' is pressed.