Having issues with Adobe Digital Editions? Here's my advice.
Step 1. Create an Adobe ID, if you don't already have one.
Go to https://account.adobe.com/.
Technically you don't need one for the laptop Adobe Digital Editions, but you do for the mobile ones. And if you want the ebooks synced across devices, you need one.
Step 2. Download Adobe Digital Editions for laptops and/or mobile devices.
Be sure to sign in with your Adobe ID!
Step 3. Go to ProQuest Ebook Central to locate relevant titles. Click the Download Book button.
You might luck out and the book is a simple PDF file. But most aren't.
On a laptop, skip through the first 2 messages about what device and needing Adobe Digital Editions. On the 3rd screen, click the blue Download button, and that should download a file with .acsm extension. Click on the file once fully downloaded, and it should open up Adobe Digital Editions, or just tell it to open that file with Adobe Digital Editions.
Was a couple more steps on the iPhone. Again, skip through the first 2 messages. Click the Download button, then click Download Linked File. In the Safari browser, the file can be found by clicking on the down arrow in a circle in the upper right corner. Then it shows you an .acsm file that's only 2km. Click the upload icon in the upper right corner and select the app to open it with. (I had to click on More and then scroll my apps to find Copy to Digital Editions.)