Head towards the marker in the central Waterfront. Interact with it to access your inFamous Paper Trail profile. If you have performed all of the steps, on the internet page, properly (determining the correct number and entering it into Delsin's phone) you will be allowed to start the eighteenth mission and it is going to concern locating Celia's apartment. Press UP on the D-Pad to start the mission.
Make it over to the rooftop of one of the taller buildings and start tracking the signal, using the phone. Head West, because Celia's apartment is in Uptown. You need to get near the balcony, high above, which neighbors the green door to the apartment. After a short cutscene, jump over to the balcony and wait until you are prompted to log on to the inFamous Paper Trail internet site.