Electronic ticketing is a method to document the sale and track the usage of the transportation of a passenger, without requiring the issuance of a paper value document. You simply print a copy of your itinerary and keep it with you during your journey.
Just present it at the check-in counter and it will be processed in the same way as if you had a paper ticket. If you misplace your e-ticket, you will need to contact Air Niugini and ask for your e-ticket to be emailed to you.