You can complete the English to Chinese part of each session by entering Pinyin or Chinese characters (Hanzi). For Pinyin, the tone mark is entered by tapping the tone mark button underneath the input field. To enter Hanzi, you will need to install a Chinese soft keyboard, which can normally be done through the settings for your phone.
However, we still recommend answering the questions by entering Pinyin rather than Hanzi! This is because Chinese soft keyboards typically require you to enter Pinyin anyway, but autocomplete so that sometimes only the first letter of the syllable is required, and they don’t require the correct tone to be entered.
This is helpful for writing Chinese in general, but makes self testing in the app rather too easy. For example, to enter the Pinyin for “好” in the Android app, you would enter “hao3”. With a Chinese soft keyboard you might just have to enter the letter “h” for the character “好” to appear in a selection menu.
If you are adding your own words to the user dataset, having a Chinese soft keyboard installed is a significant advantage, but even then not necessary if you just require the Pinyin romanization. Without Chinese characters you will only be able to have one entry for each distinct Pinyin word (including tone marks, so for example “xin1” and “xin4” can be separate entries).