"I show him the mouse."
Translation:Εγώ του δείχνω το ποντίκι.
Try accessing them via the website https://www.duolingo.com/ -- you may have to "request Desktop site".
If it doesn't work in your mobile device's normal browser, I've heard that using the Puffin browser make convince the website to show you the tips and notes. (But I don't have first-hand experience of that.)
On the website, the tips and notes "hide" behind the light-bulb icon on the little window that appears once you have selected a unit.