I'm not entirely sure what the problem is here, are you missing the overlay panel in CC2015 or the Folio Builder panel in CC 2014? .. or both?The Desktop Content Viewer as you know it in DPS Classic is no loger supported in InDesign CC 2015. You should still be able to see the Overlays panel in the 'Window' menu. If not please install manually (Installation and setup for AEM Mobile tools )If you use CC 2014 however, you should be able to see the Folio Builder panel that has a preview functionali...

A couple more things. The Desktop Web Viewer shows only published content, not preflight content. To view your content in web viewer, you need to publish it. See Publishing content for AEM Mobile apps.​In your screen shot, you're trying to sign an app, which isn't necessary at this stage. Instead, you can use the preflight app. See Use the AEM Preflight app to view AEM Mobile content. When you're ready to build the app, see this article: Build AEM Mobile apps for iOS devices​