The GUI isn't available until 3rd party developers release it in May --- currently it's command line only.
https://github.com/TobyLobster/Inform for MacOS, maintained by Toby Nelson
https://github.com/DavidKinder/Windows-Inform7 for Windows, maintained by David Kinder
https://github.com/ptomato/inform7-ide for Linux, maintained by Philip Chimento
https://github.com/TobyLobster/Inform for MacOS, maintained by Toby Nelson
https://github.com/DavidKinder/Windows-Inform7 for Windows, maintained by David Kinder
https://github.com/ptomato/inform7-ide for Linux, maintained by Philip Chimento