Thank you to Duke University for graciously allowing re-use of some of the content from their guide.
On iPad/iPhone or Android Devices:
The default web browser on some Android devices, including the Samsung Galaxy series, does not download epub files.
If your device never downloads the file (check the downloads option in the menu to make sure), you may need to download an alternate web browser. Firefox and Chrome are both available via Google Play and work well for downloading files.