If you want to select which games you want to play, you have to:
1. Go to the "You" tab.
2. Tap on "Favorites". 
3. Tap on the three dots near the group for which you want to select the games.
4. Tap on the "Choose Games" button. 
5. Choose the games you want to play for:
- learning words
- learning sentences
6. Tap the "Save" button.
Note: At this point in time, the Favorites feature is available only upon Paid Subscription and only on Android devices.
How do I subscribe?