While the application is opened, right click on its interface and go to Settings as well as Help. The Help section will provide a fast guide on how to set it up. The settings section is more advanced since it contains additional options to configure. There is also an Active Time option, but it's nowhere mentioned how it works, which means that you will have to test it.
Additionally, check the TelePrompter product from the same developers because it appears it's a little more advanced than Dream Scroller.