A) You create a database, create a database user and password. These could be the same as your previous installation. Put these values into your wp-config.php file.
B) Using phpmyadmin, you import the .sql file. You may need to edit the backup for various reasons, such as removing its "create database phrase", OR to break the loading time down to an acceptable limit, maybe separate out the big tables, maybe split a table into separate loads, if you keep them in order the database wont know the difference.