This add-on allows students to have a sneak peek at lessons prior to enrolling in a course.
Once you have enable the Course Preview add-on, go to Masteriyo > Courses > Edit a Course. Now, edit a lesson for which you want to enable the preview.
In the lesson editor, you will see the button to enable the preview. Enable the preview from this button.
Once you have enable this, you can see a button on the Course Page > Curriculum > Lessons.
The students can preview the lesson via this button.