Fortbyte 76 is located on the first floor of the Historical Building, behind a Historical Diorama in Neo Tilted. Epic Games has been releasing new bytes in Fortnite every day so far. They are not released in numerical order. Below is a YouTube video of the exact location of the Fortbyte.
Fortbyte 76 Location
Above is a video of us arriving at the location. Luckily we didn't get farmed by someone with a shotgun before we got to pick it up. Doing challenges in Team Rumble just in case we fall into a sweat trap.
Hope this helps... Even though there are probably 1000 other guides out there. For weekly challenges check out our Cheat Sheet guides. Good Luck and Have Fun!