Just in a few easy steps you can create your own padlet account for free. As soon as you have it, start creating and sharing your walls with your students. A whole new world of collaborative writing is waiting for you!
The walls can be filled with "sticky-notes" in which students narrate their own short story about a given topic. Or it can flow as a continuous stream so that each student continues the story of the previous participant. This latter option is great to practise cohesion and coherence and, as a bonus, it is promotes creativity: the resulting stories usually have quite unexpected turns.
As for the visibility, the options range from restricting the access to your walls so that only your students can view and modify them -- thus providing them with a secure environment -- to make them totally public so that anyone can see them (and even contribute to them!).
Watch this tut to find out how to create your own walls. You'll be amazed at how easy it is.
Your students can watch this video to see how to add a post to the wall and share its URL.