If you are doing the course on iOS or Android, you cannot currently access the Tips & Notes through the app. To access the Tips & Notes, you will have to access the course using a web browser at https://www.duolingo.com/. You can still do it on your mobile device, but you will have to use the web browser instead of the app (or you can do it from a computer). When you click on a Skill, it will expand to reveal a Start button and a light bulb (and a key, which is not pictured below, but is how you can test out of a Skill).
Some learners translate Klingon to English simply by translating from the end of a sentence to the beginning, rather than understanding Klingon word order.
So we are fairly strict about word order in places such as A B je, which means “A and B”.
The meaning may be similar or often identical to “B and A”, but the writer may have meant something by putting A first, and this is another reason we insist on the correct word order.