Two-Step Authentication for iCloud
Enable the app-specific password for SmoothSync for iCloud
Apple introduced new security features to iCloud, including Two-Factor Authentication and App-specific passwords. App-Specific passwords are generated per app and and can be used instead of your Apple-ID credentials. This guide will help you to set them up for SmoothSync For iCloud.
Important: Starting on October 1, 2014, App-Specific passwords will be mandatory to login at iCloud using Third-Party apps.
1.) Open https://appleid.apple.com (1) and log in using your Apple ID credentials (2)
2.) The site will sent an verification code to one of your Apple devices.
3.) Enter the code that's been sent to the device.
4.) Open "Password and Security" (1) and select "Generate an App-Specific Password" (2)
5.) Choose a label that will help you identify the password, e.g. "SmoothSync".
6.) Click "Generate Password".
7.) Use this password to login with SmoothSync.
That's it. If you have any difficulties don't hesitate to send a mail to support@dmfs.org with a description of your problem.