Downloaded e-book in Adobe Digital Editions 4.0 (mac laptop) will not appear/sync with iPad OverDrive app

I just downloaded an e-book from a third party supplier.  The e-book supplier said to download Adobe Digital Editions 4.0 to put the e-book on my laptop, and then said I could sync up to 5 other devices and sync the library of the OverDrive app on those devices with Adobe Digital Editions.  I have downloaded the OverDrive app to my iPad.  I have signed up for an account.  According to the app, it is synched with my Adobe account.  However, the e-book that appears in my ADE library does not appear on the OverDrive app library.  How do I rectify this?  Many thanks.  -Matt