It has not been officially released yet, it's still under development and it has very limited backwards compatibility with Orbiter 2016. Not that much has changed for the end user, so if you're not really a add-on developer then, this is not for you.
You can get testing/beta builds from github, but if you want to complain to much about bugs or worse, consider yourself warned, its no official release for end users with expectations. You can also use this to test add-ons for the future or try orbiter in x64 or Linux.