Need Steps to Install multisite configuration using only drush. i.e multi-site install having different database
Try:

drush site-install --db-url=mysql://USER:PASS@localhost/DATABASENAME --sites-subdir=sitename

You may also need to add --db-su and --db-su-pw if necessary to provide the right credentials to create the database if the user specified by USER:PASS does not have permissions to do this.

See drush help site-install for other useful optional options you might want to specify, e.g. site name, admin account details and so on.