For group or unlimited license, the extension can be distributed through the Microsoft Education or Business Store
Windows store for Education can be found here.
Windows store for Business can be found here.
Microsoft deployment instructions for apps and extensions can be found here.
There are 4 mechanisms for distributing apps through the business and education stores
- Distribute apps using your private store
- Assign apps to employees
- Distribute apps with a management tool
- Distribute offline apps