I just explained how to add fonts. Just double click on any font files.
There are a range of Chinese fonts just scroll down to them:
Adobe Fan Heiti
Adobe Fangsong
Adobe Heiti
Adobe KaiTi
Adobe Ming
Microsoft Tai Le
Microsoft Yi Baiti
MingLi
PMingLi
SimSun
Sinhala
STHeiti
STFangsong
STKaiti
etc
To type in Chinese choose your input method:
Menu > Apple > System Preferences > Keyboard > Input Sources > check Show Input menu in menu bar > click on + > Add Chinese (Simplified/Traditional) whatever method you want
You can choose your input method from the right hand side of the Menu bar when you need them.
Peter