Unit 2 Chapter 1 Lesson 13 - Sharing the student website

When one of my students selected the “Share” button it said that he did not have permission to share his website and he should talk to his teacher.

How/Where do I make it so that the students can share their websites?

Here is an article showing how to allow or disallow student sharing

Thank you.
I knew I saw these settings somewhere. The article was very helpful.