Editorial Quota is a Wordpress plugin to manage posts' redaction. You will be able to set a quota of post to make by month and check if the authors made them.
To install Editorial Quota with Wordpress, download the .zip file, go to Wordpress then Plugins > Add New > Upload and upload the .zip. Then active the plugin and you're done \o/
To install Editorial Quota with FTP, just upload the directory to wp-content/plugin in your server.