To add staff member as Library Member, go to Library > Add Staff Member after that to search specific members enter the staff name and click on the Search button then click on the + button from the Action column, at the click of this button it will open a modal, here enter Library Card Number and then click to Add button.
The added staff member will be shown in the green color row in the staff member list. To remove staff membership click on the Surrender button present in the Action column.