In our course approval criteria we list some prerequisites that apply to teachers of approved courses.
New teachers have to teach at least five Bach Centre-approved Level 1 courses before they can teach their first Level 2. They also receive extra training.
Similar rules apply to new Level 3 teachers.
So your first step to becoming a Level 3 teacher is to become a Level 1 teacher.
Look for Level 1 teacher training opportunities in your country.