We were on the Jade from Piraeus a few weeks ago. The first queue at the port, they check your passport and vaccination records, you then leave your suitcases here (NCL take care of them) and then proceed to a large tent near the terminal for the testing. If you've pre-registered with Eurofins you'll jump part of the queue (compared to those who haven't registered). You then get a coloured label and sit down. There are staff offering water to drink at this time. When they call your colour you go to a small test area, do your test, then go to a separate waiting area. Keep watching for your number to come up on the board, and when it does you go to the desk then get a pink wristband and are then allowed to proceed to the boarding tent (for cabin cards, security, screening, etc)