A short one just to remind me, more than anything else.
Log into MySQL with the command
mysql -uroot -p
To see all existing databases, use
show databases;
To create a new database, where xxxx is the name of the database you want to create
create database xxxx;
To add a user, where yyyy is the username, and zzzz is the new user password
create user 'yyyy'@'localhost' identified by 'zzzz';
To assign the new user to the new database (xxxx is the database, yyyy is the username)
grant all on xxxx to yyyy;