Assign lesson to Group

Financial Crim…
Hi I don't think what I'm trying to do is complicated but somehow I'm having trouble. I want to create a structure of Lessons>Courses>Classes but I cannot find anywhere in the manual or in the Forum how to link these various things together. I did think that perhaps I needed to put lessons into a Group using Organic Groups . I ticked the "Group" box on the Lesson Content Type but I can't find Lesson anywhere as a field or as a Group and it's not showing the Drop box when I create a new lesson. I'm reasonably familiar with Drupal (D7) but I've never used Organic Groups. Can someone please point me in the right direction to achieve my Lessons>Courses>Classes structure, please? Thanks.