Transfer ebooks to a Sony reader PRS T1

Hi, I have a Sony PRS T1 ereader connected to my imac. I have  downloaded a DRM ebook using ADE with logon.  In the library I see the book and can read it on my imac (authorised) but my Sony reader doesn't appear in the library when I launch ADE with the Sony connected.  How do authorise the ereader and  transfer my new book if I don't see the reader in library listing?