I'm going to assume this is a domain. You do not need to use administrator credentials, but the folder you are scanning to needs to have full access for the credentials the scanner will use (or full access to 'Everyone'). Unless something has changed this must be 'full access' - simply enabling 'read' and 'write' attributes doesn't work.
Simply enter the host name and the name of the shared folder. If it is a subfolder to another share use 'share\folder'.
On a domain, user credentials must be 'DOMAIN\user' where the domain name is all capital letters.
