Make sure that you followed all the steps on the website (the main objective was to "remove" the letter from the drone) and go to the marker located in the western part of Pioneer Square district. Once you reach the place and the game successfully connects with your inFamous: Paper Trail profile, press up on the D-pad to start the third mission.
Head back to the theater (Crocodile) located in the south-western part of Paramount district. This is an area where you have already been, when you examined the first crime scene, so you will easily get to the destination point. Once you reach the place, start by taking care of drug traffickers standing in front of the main entrance to the theater. Defeating them is very simple, because they do not have any extraordinary powers.
Once you win the fight, walk up to the theater's front door and wait until you get automatically moved into the building. Go to the room where you dueled with Fetch during one of the main missions and find another victim. Of course, you have to examine this crime scene, namely, take pictures of three different parts of the man's body.
Once you take the pictures, watch a short cut-scene with a "paper rabbit" and examine the exact spot where this character has just been standing. This will allow Delsin to take find another origami dove. The only thing left for you to do, is to leave the building, thus automatically sending the newly obtained exhibits to inFamous: Paper Trail.