@Alvenchipmunk,

You can type in Chinese right on Popup Chinese by clicking the green "en" button right above the comment box。 That will switch you to Chinese input mode. A box will appear that will show potential Chinese words whenever you type a word in pinyin. Screws up copy and paste for me, but is pretty useful.

To type Chinese in any program or on other websites, you'll need to install a Chinese input method editor (IME). I'm a windows users and recommend the free one released by Google and available here:

http://www.google.com/ime/pinyin/

Brendan has recommended QIM for Mac users in other threads. I've never used it myself, but have heard good things about it from other Mac users as well:

http://glider.ismac.cn/RegQIME.html