Generate text translation on Android
On the home screen of the app, you'll see the text input field. It includes two sections: the top field shows the language you are translating from, and the bottom field displays the translated result in the language you are translating to.
To change either language, tap the language icon (flag) next to the corresponding field.
Tap the input field and type the text you want to translate. Then tap the "Translate" button, and the translated text will appear below.
If you want to swap the input and output languages, simply tap the switch icon
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Generate text translations on iOS
In the first/top field, enter the language that you want to translate from. To select a different input language, tap on the language icon (flag).
The second/bottom field will show the translated result. To select a different output language, tap on the language icon (flag).
You can use the swap icon 
to change between languages.