First off, you want to install MAMP or MAM Pro on your computer. Go to download it at http://www.mamp.info/en/index.html
Second, open a terminal window
Third, type in /Applications/MAMP/Library/bin/mysql --host=localhost -uroot -proot;
(Don't forget to type ";" to end a commend.)
And now you can start using MySQL commands. Good Luck!