Credentials come from the regional office, not from a panel
The customer identifier and password a PTT Kargo connection needs are not values you generate yourself in a web panel: they are issued by the PTT regional directorate you are attached to. It resembles the regional office logic of Yurtiçi Kargo; setup is a request process rather than something completed on a single screen.
A third field, the service user, takes a fixed value in most installations and that default applies when it is left empty. Trying to fill it in and hunting for a value is unnecessary.