Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, a web toolkit designed to help citizens, conservation practitioners, municipal decision-makers, researchers, educators, and students advance knowledge and stewardship of fresh water. New to EnviroDIY?Start here
You should be able to copy-and-past the URL of the json file into the appropriate place in the IDE Preference window and then the IDE will fetch the file and load it properly. We haven’t made any changes to the board definition files in several years, so there shouldn’t be any problems. What version of the Arduino IDE are you using?
The Arduino IDE 2.0 is still a beta release and is so new that we haven’t done extensive testing to make sure all our EnviroDIY-related instructions, libraries, and sketches work perfectly. So I would recommend you use the regular release of version 1.8.13 (available here: https://www.arduino.cc/en/software) instead of the beta version.