Actually, most of the STACK experts hang out in the Maths tools forum.
The best way to start is to work through the Authoring tutorial: https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Authoring/Authoring_quick_start.md
The best way to start is to work through the Authoring tutorial: https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Authoring/Authoring_quick_start.md