It's on your device...pc, phone etc. And it's very easy to access:
HOW TO GET THE GREEK KEYBOARD These links will not only show you
-how to get the Greek keyboard but also
-how to find the Greek letters on it, how to add accents etc.
-It will also help you learn the alphabet and where to find other help.
TIPS TO HELP YOU LEARN + HOW TO REPORT A PROBLEM
And here is another to help you navigate Duolingo
MODERN GREEK RESOURCES How to get the keyboard and much more. (alphabet, ...853,resources, etc)... ++..... https://forum.duolingo.com/comment/22040507