How do I compile my c++ project on Mac OS X?

Okay, so I discovered emacs on my Mac and I created a random little project but I tried compiling it like I did at school (we would do ‘M-x compile’ and then where it would say ‘make -k’ we would delete and put g++ ‘test.cpp’ or whatever name of the project) but when I tried that at home, it said “/bin/bash: g++: command not found” how do I make it so it compiles?