Use the fontspec package with XeLaTeX. We will document XeLaTeX RSN. For now here's a simple example:
\documentclass[11pt]{article}
\usepackage[cm-default]{fontspec}
\begin{document}
{\fontspec{Kai} 你好吗}.
\end{document}
Information Technology
In most instances, XeLaTeX is easier to use than babel. To avoid unnecessary frustration, see the XeLaTex instruction section, which applies to all languages, not only Greek.
This is not the only way to type Greek in TeXShop. See the Babel instruction page for another option.


\usepackage{fontspec}
\setmainfont{FONTNAME}
\setmainfont[Ligatures=TeX]{FONTNAME}
\newcommand{\greek}[1]{{\fontspec{FONTNAME}#1}}