im in need of some major help....i need to create a payment system for a pretend electric company. i have designd this system using classes of:

customer (parentclass) - billed customer (subclass), prepaid customer (subclass)

payment class (parent class) - card class (subclass) bill class (subclass)

then there is also a class needed to create a report of the payment. eg the amount paid and time online.

i also have to have a GUI for this system...

i have no idea how to create this system. i am using netbeans to implement this. any idea?
im so confused about it all and just cannot seem to be able to get through it.

thanks for any help, any and all help is appriciated as im struggling so much