Head to the facility and get the helicopter. Fly to the jump marked by a yellow ring. Now line up your parachute jump while you are still far out so you will only need minor adjustments for the vertical axis. Brake and accelerate properly to keep the roof close to your screen, while underneath your feet. Use a hard brake when you are about to land.
After landing, run to the computer and run hackerconnection.exe. Clear both of the simple minigame programs.
Now use Michael to sweep out the center, right, and upper right areas of the skylit room, all while in cover.
Swap to Franklin and clear the left area. Blast away as much as you can with the assault shotgun once the smoke screen appears. Keep blasting until the smoke clears up.
Move from cover to cover using the assault shotgun along the halls. Rappel down the wall, hide behind cover, take the rocket and obliterate the gunship.
Head to the ground, get the ambulance and exit.