Go to Language Support -> Install/Remove Languages…
Select Chinese (traditional) and Apply Changes
In the Language Support window, select ibus in Keyboard input method system
After logging out, IBus should start automatically when you begin a new session.
Go to the IBus preferences and modify Show language panel to Always.
Go to the Input Method panel and Add the Chinese – Pinyin or/and Chinese – Bopomofo method(s).
Choose an input method, e.g. Chinese – Pinyin. Write some text in a window, the method toolbar should appear. You can select simplified or traditional Chinese input thanks to that toolbar.