If you want to create your own flash cards or add Japanese words to the dictionary you will need to enable Japanese text input in Mac OS X. To do this open System Preferences and click on the International icon (The United Nations flag).
In the International Preference pane click the Input Sources tab and enable the following items:
Also check the 'Show input menu in menu bar' option if it is not already enabled. This allows you to switch between English and Japanese text input.
To test things out, open TextEdit and switch the input selection from English to hiragana in the Input Menu. Now try typing 'hiragana'. You'll notice as you type the rōmaji for each kana it gets replaced with the corresponding hiragana. You should see ‘ひらがな’. You will see an underline beneath the word, press return to confirm or the down arrow key to display a listing of possible kanji and katakana alternatives.
To type ‘ん’ type an ‘n’ twice. Holding down shift or turning on caps lock will let you type in katakana without switching specifically to the katakana input method. The system will automatically insert small tsu (っ) and small ya, yu and yo (ゃ,ゅ,ょ) characters when you type a contracted syllable or type a double consonant. Similarly with certain katakana sounds, small vowels will automatically be inserted in response to specific letter combinations. For example typing ‘WI’ produces ‘ウィ’.
To revert back to English or your preferred language simply choose the relevant option in the Input Menu.
Another option you can use to enter kana is the Kana Table. This is available once you switch your input method to hiragana or katakana in the Input Menu. The Kana Table is a panel containing all the hiragana and katakana characters as buttons. You simply click the characters you want to type. It also includes some Japanese punctuation marks. The three tabs along the top of the palette let you choose between hiragana, katakana and rōmaji.