I Googled your question and this is what i found:
"The .acsm file isn't the book - it a purchase ticket that allows you to download the book.
In Digital Editions you can find the path to the book in the Item Info dialog. You can bring up the Item Info dialog from the Reading Menu (in Reading View) or pressing Ctrl+I (Cmd+I on the Mac)."
Hope that helps!
(You may ignore Step 1, but I highly recommend it as it makes it easier later on._
Step1. On your PC create a folder with the name of your Library in a place where you can conveniently locate it.
Step 2. From your Library's website, download the book file to the folder you created in Step 1. If you skipped Step 1, it will probably go to your "Downloads" folder.
Step 3, After download (which will take all of 5 seconds), open the folder where the file is located using Explorer.
Step 4. Double click the file name, and the book will open in Adobe Digital Editions. Be aware, that when you downloaded the first time, you were downloading permissions for the book and when ADE opens it will actually download the book, so you must be connected to wifi.
Step 5. Connect your NC. It should appear in the left menu of ADE. It may say, "NC" or "media."
Step 6. Drag the book over to your NC designation in the menu (the red x will become a green + when you are over the right directory) and drop the book.
Step 7. Unmount your NC and open "Library" "My Files" "Digital Editions"
Part of the reasoning for creating a folder for just your library books is that when they have expired, you must go and delete them from your computer, and your NC. It is easier to do if you have them in one place and clean them out as you acquire new ones.
Hope this helps!
Thanks Jeremy! Found this discussion via google. Your steps worked perfectly for me.
That worked just fine. Thanks Jeremy
Thanks man, that really made it easy. I fiddled around forever trying to drag that book all over the place in Adobe Digital Editions but never over my nook icon. When i dragged it over my nook icon, it turned green and dropped right in. Great help with your post.