Sideloading is a process that lets you use iTunes to manually add a .folio file to the Adobe Content Viewer. With the newest release of tools (Drop 12), sideloading is no longer available. Instead, if you sign in using the same Adobe ID on the viewer that you use in the Folio Builder panel, you can download any folio you have access to. For the first download, this process can be time-consuming, especially for larger folios. However, after you download the first time, only the new folios are downloaded during an update.
If you want other people to preview your content, use the Share command in the Folio Builder panel to share the folio. To view the shared folio, users need a copy of InDesign CS5 or CS5.5 with the free Folio Producer tools installed and a free Adobe ID account.