Desmond is being sent out into the world. His team has found the first of a number of power sources that they need to power the Temple. He is being set to Manhattan. He is given an earpiece and a Remote Camera.
Go forward and climb the ladder in front of you. Head on forward and free run through the machine room with the yellow piping. Run along it to the high opening in the fencing. From there just keep on moving forward. Follow the illumination to find your path on outside.
Once outside turn to the right and jump for the scaffolding there. Climb on up and follow the yellow beams up onto the crane platform. From there climb on up the arm of the crane. Run to the end and jump onto the beam suspended in front of you. Just continue on forward on the jutting beams in front of you. Continue on forward until you get to the next platform you can walk on.
The trail seems to dry up here. The reality is you need to climb the red beam in the middle of the platform with the wiring by it. Climb upwards following the wiring running to the next floor. Once there then run across it. Go on over the giant spindle and run at it to slide underneath it. From there run for the yellow ramp that will lead you to a few t-bars to jump across into a pipe. Run on through then head over to the right, climb up the pile of beams then turn to the left and jump for the suspended beam.and through another pipe.Head over to the right and go across the beam.
Once across it, then climb on up this slated surface. From there head across the floor and jump for the suspended beam across from the flood light. Take that across to get to the rooftop and the crane there. Once on the roof just head on up the crane and make for the lit-up crane.
Just run for the top of it and get into position.
Jump when you are ready but be sure to listen to Rebecca to use the parachute. As she said, timing is critical. From there just steer Desmond toward the Helipad to have a good and safe landing. This leads to a cutscene with Desmond acquiring the first power source. His robbery is interrupted when Daniel Cross makes an appearance. Desmond escapes from the office with the power source and then his team returns to the Grand Temple.
Back in the Temple
Once back in the temple head for the crumbling Staircase. Enter the room to trigger a cutscene with Juno who explains something of this temple's purpose. Climb the staircase inside the room afterward. Go froward to the broken walkway. There turn to the left and make your way upwards along the inside of the room. This will lead to a console where you can insert the first power source.
Take some time to talk with everyone else then head into the Animus to resume the life of Connor