South Parker Square ctOS Tower
From the street to the north, head down the alleyway next to the Ethiopian Cuisine restaurant and look for a yard on the right hand side.
Hack the forklift then use it to climb up onto the roof of the building.
Continue along the roof until you reach a metal walkway then hack the lift below to raise it.
Use the lift to reach the next roof then climb up the fan units to the walkway and use the ladder.
Hack the camera inside the Tower area.
Look right and hack the Switch Console to unlock the gate.
Now head through the gate and unlock the Tower.
East Parker Square ctOS Tower
Follow the track up to the top of the hill to find the entrance to the Tower area.
Vault over the crates and hack the camera on the opposite side of the building.
Hack the forklift in the next area to reveal a camera behind it, then hack into that.
Hack the Switch Console opposite to unlock the gate.
Go back the way you came in, then through the gate and up the ladder.
Drop down the other side and unlock the Tower.