The correct command looks like: mysql -u root -p databaseName < /path/to/your/b3/installation/b3-db.sql
It's maybe easier to understand in single steps:
1) Connect to MySQL: mysql -u root -p
2) Enter MySQL root password
3) "Use" the correct database: use databaseName;
4) Now import the B3 MySQL layout: source /path/to/your/b3/installation/b3-db.sql;
The database you need to create in phpMyAdmin or HeidiSQL first.
Install phpMyAdmin: either download it directly: http://www.phpmyadmin.net/home_page/index.php
With this step you can just extract it in /var/www.
Or do: apt-get install phpmyadmin (this will make a "special link" to your phpmyadmin, like http://37.59.111.62/phpmyadmin)