Apple has sent an email to users of its two-factor authentication system reminding them of an upcoming change to the feature that will take effect tomorrow. Originally the requirement for app-specific passwords was supposed to start on the first of the month, but Apple has informed users that it will begin tomorrow instead. The system to generate and use these passwords is already in place.
App-specific passwords allow you to log into applications that don’t support two-factor logins, such as most email clients or other apps that may want to access your iCloud data. You can create these one-time-use passwords from the Apple ID website. Once you’ve generated the password, just plug it into the app you want to use and you’re all set.