I downloaded ADE to my PC windows 8 laptop; when I go to public library to check out ebook it does not show up in ADE for me to then put it on my NOOK. So why is it not automatically downloadng to my ADE?

I downloaded ADE to my PC windows 8 laptop; when I go to public library to check out ebook it does not show up in ADE for me to then put it on my NOOK. So why is it not automatically downloadng to my ADE? Can anyone help?