First install the plugin using WordPress auto-installer or download the .zip file from wordpress.org and install it from the Plugins section of your Dashboard or copy wordpress_file_upload directory inside wp-contents/plugins directory of your wordpress site.
Activate the plugin from Plugins section of your Dashboard.
In order to use the plugin simply go to the Dashboard / Settings / WordPress File Upload and follow the instructions in Plugin Instances or alternatively put the shortcode [wordpress_file_upload] in the contents of any page.
Open the page on your browser and you will see the upload form.
You can change the upload directory or any other settings easily by pressing the small edit button found at the left-top corner of the upload form. A new window (or tab) with pop up with plugin options. If you do not see the new window, adjust your browser settings to allow pop-up windows.
Full documentation about the plugin options can be found at https://wordpress.org/plugins/wp-file-upload/other_notes/ or at http://www.iptanus.com/wordpress-plugins/wordpress-file-upload/ (including the Pro version)
