1) You jump to the star system where you are expected to meet Nemo.
2) You fly around in the star system with supercruise a bit, not too fast, not too far, not too slow either - if you are too slow you can't see ships.
3) You wait until you get a message from Nemo, probably complaining that it took time to find you.
4) You go to left hand panel to select Nemo, then you know which of the ships on radar is Nemo.
5) You wait until Nemo gets a bit closer. You can try to help him by getting closer to him, but don't go too far or too fast.
6) Nemo will send you a message to "follow" him and exit supercruise, leaving behind a "low wake". The reason for the low wake is to meet Nemo at short range, so Nemo can send you the important data directly, short range, ship to ship, without longer range transmissions and risk of other people listening.
7) You go to left hand panel and target Nemo's low wake signal.
8) You approach Nemo's low wake signal, not too fast or you will overshoot.
9) You drop into Nemo's low wake signal just like you would drop from supercruise to a station. Problem can occur if you do not manage to drop into Nemo's low wake before the low wake disappears. In this case, slow down, exit supercruise, then enter supercruise again. Nemo will appear again and low wake again and you can try to reach the low wake signal again.
10) You slow down immediately after exiting supercruise. Nemo will be close by. If you don't slow down, you might crash into Nemo's ship.
11) Nemo will send a message, telling you to deliver the data to another station in another star system. When that message appears, Nemo has sent you the data.
12) You travel to the station where you need to deliver the data.
