Ride the next elevator up as far as it can go. Enter the building, and head up the elevator to the fifth floor.
Put on your jetpack-enabled Power Armor suit, and Fast Travel to the Mass Fusion Building, north of Goodneighbor near the Old Corner Bookstore. You may also want to bring along some Ultra Jet, Buffjet, or Nuka Cola Quantum as well. Jetpacks can be crafted as a torso mod in the Power Armor workbench, but require Rank 4 in both the Science! and Armorer perk abilities. Since there is no direct path to reach this floor, players must jump to this upper level instead by using a suit of Power Armor equipped with a jetpack. The Freefall Armor is located on one of the top floors of the Mass Fusion Building. Other Useful Fallout 4 Guides from USGamer: Follow along to find out how you can get this armor yourself. Getting this rare armor requires certain equipment and tricky maneuvering. The Freefall Armor is a pair of left and right leg pieces that prevent all falling damage on your character.
Of all the rare items to be discovered throughout the wasteland, the Freefall Armor legs are likely the best armor pieces to have in one’s arsenal.