Section 5.9 of the MySQL Manual: User Management

Use the GRANT statement to create new user accounts. e.g.:
Code:
GRANT ALL PRIVILEGES ON *.* TO 'user1'@'localhost' IDENTIFIED BY 'a_passwd';
This will create a user account with the username "user1" allowed access to all databases on the server with the password "a_passwd", which will be encrypted.

So with this you will need the following SQL statement:
Code:
GRANT ALL PRIVILEGES ON *.* TO 'greg'@'localhost' IDENTIFIED BY 'a_passwd';