Apple ID as an AIM account set up
- Open the messages App on your Mac.
- Click in the menu bar, click "messages" -> "settings" and then switch to the Tab "Accounts".
- Click on the " + " to add an Account. Select in the appearing window, the item "Other E-mail Account".
- You set the account type to "AIM", enter your iCloud login data and click "Create".

AIM account setup
Read also how you Mavericks, your iCloud account settings change.