If you simply want to launch emacs inside a Terminal window, type as follows.
$ emacs -nw [filename]
The "-nw" option stands for "no window".
If you want to launch Emacs in another window (or as a separate application), install Emacs for Mac OS X as follows. With this, you can use commands from menu bar, and also use Japanese.
alias em="/Applications/Emacs.app/Contents/MacOS/Emacs"This way, one can launch multiple emacs by:
$ em foo.txt & $ em bar.txt & ....
2013-11-16 Taku Yamanaka