See
Books on Board: Astak EZ Reader Help. The EZ Reader is a Hanlin V3, like the ECO Reader (although the photo is of a Pocket Pro, a Hanlin V5, but the process is the same).
You don't have to use Desktop Adobe Digital Editions to copy the ebook files to your ECO Reader, unless you want to. Once the device is authorized, you can put them in whatever folders you want via USB (just like DRM-free ebooks). On your PC, the files are in My Documents\My Digital Editions.