I need to use a special keyboard on my device (Japanese, Korean, Chinese).

Great idea! See the relevant instructions below. Note that the exact steps may differ by device.

iOS

1. Open Settings, tap General, then Keyboard.
2. Tap Keyboards (with an "s"), then Add New Keyboard.
3. Scroll down to the language you are learning, then choose any preferences.
4. Tap Done at the top right.

Android

1. Open the Google Play Store and search for "[your language] keyboard".
2. Install the Google input app (e.g. Gboard) and go through the setup instructions.
3. Go to the Language & Input section of your device settings and turn on the new keyboard.

For other languages, it is usually possible to add them to your device's multilingual keyboard. Have the alphabets you're learning right at your fingertips!