It should have associated .acsm files with ADE when ADE was installed. If not:
- For some reason, ADE cannot open them using standard ctrl-o
- It can open them if you drag-drop from explorer
- It can open them if you do an 'open with' in explorer and choose digital editions
- and if when you do the 'open with' you choose ADE as the default program, it should do the association so it automatically opens them right in future.