When you log on to your LearnWorlds school as an admin you will see an all-powerful "Manage your LearnWorld" button on the top of each page. By clicking this on any page you enter "edit" mode and you can start making changes. At the same time, an admin menu appears on the left hand-side of the screen, giving you access to the Site Settings, the learner admin, your sales records, analytics and settings for the different parts of the application. 

If you want to go back to the Preview mode (seeing what your students will see) than simply click again on that same button (now sporting a "Preview" name).