About creating database

I'm trying to set up the initial playground for the MU install, as a newbie I need to confirm some details, please correct me if I'm wrong.

1, It seems that the first step is to creat 16 or 256 databases and grand the privileges to a database user, I use the tool on
http://db-tools.wpmudev.org/db_sql.php
And run the generated script as root, add 16 databases to the database, they can be seen if I login to phpmyadmin as root;

2, To modify the db-config.php file I use the tool on:
http://db-tools.wpmudev.org/db_servers.php

and change the file accordingly, like:
add_db_server('a', 'dc1', 1, 1,'174.*.*.*','localhost', 'mu_a', 'wpmu', 'mypassword');

I've done this step.

3, I assume the database user "wpmu" needs the access right to read and write those 16 or 256 databases, but I've no idea how to write this mysql script. And I don't know where to run the script. Please show me a demo, if I'm wrong in the previous 2 steps please tell me the details, thank you.

p.s. What's this page for?
http://db-tools.wpmudev.org/db_array.php

Should I put the "array" to somewhere?