Once you create a Group, VoiceThread provides you with a join link that you can email to the people you'd like to join or simply include in your course management system, behind the authentication ensuring that only your enrolled students will have access to it. I make joining our VoiceThread group a required activity the first week of our class. When a student clicks on the link, s/he is taken to a page that asks them to Sign In or Register for VoiceThread. If they already have a VT account, they can access their existing account and they're automatically made a member. If they're new to VoiceThread, they just click on "Register," complete the form and in a single swoop, their account is created and they become a group member.
I can easily check to see who has joined the group by accessing the group list from within my VoiceThread account too. Each week, as I prepare my content for the next unit I simply share our VoiceThread activity with the class group and embed it in my course management system. Students click on square button included in the embedded VoiceThread that says "Sign in or Register" which allows them to authenticate into their own VT account without leaving the CMS. Doing so makes the embedded VT visible and lifts the message, "You do not have permission to view this VoiceThread," which is what a non-authenticated user sees." Using the group feature is an easy way to ensure the content remains secure and prevents students from sharing content with non-enrolled students. Now, I am fully aware that there is a very good argument for requring our students to participate in the open web -- and I do support that argument. But if we have the interest in supporting student privacy, for institutional reasons or due to the nature of the content being discussed in the class, understanding how to manage it effectively is an important part of teaching with emerging technologies.
Learn more about VoiceThread groups here. Below is a brief video that illustrates how and why to create a VoiceThread group: