Go to Melanie through the elevator first, then head up to the CCO's office. After the cutscene, turn to the corner and receive level 2 security access. Melanie will speak with Olivier alone. During that time, John will put a new waypoint in your map. Head to the corridor next to the receptionist then continue downstairs. John will now give you LV2 access which will allow you to open the door.
Find the LV2 door along the corridor to reach the security room. Operate the console and you'll have to hack it using a new method at this point. Open the tutorial again if you need assistance. Select 2-5-7 to get the target number in this sequence and hack the console successfully.
After the scene, leave the security room and make your way to the open window. Wait for the gondola to arrive then use it to reach the CCO's office terrace. Head inside the office and hack his computer to get the shareholders meeting schedule. This will also count towards the number of computers hacked. Wait for the receptionist to leave then head to lobby via elevator.
Deliver the file to the courier in the lobby you can now return to the animus and resume your simulation. However, with your new access, you can explore the previously inaccessible rooms for more Sticky Notes and hackable PCs. Do this at your own pace as you see fit.