So, you use more than 1 language as the input type method on your Sony Xperia Z device and want to use mutiple languages? Add language to Xperia Z Keyboard by doing as follows:
1. Open Settings application
2. Under Personal settings, go to Language & input.
3. Considering you are using the default keyboard on your Xperia device, tap the settings icon next to the Xperia Keyboard.
4. Open Languages followed by Writing Languages to add more languages
5. Now select the languages you want to use as input method