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
Below are two screenshots. One of the Fortnite map and the other is us standing by the byte 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!