JQuery html5 download plugin. How to use it?

I don't know the plugin, but basically you need to set the url where the files should be sent (see example.html file on github):

$("#upload_field").html5_upload({
    url: /*PATH TO PHP FILE.php*/,
    ...

The PHP file depends on what you want to do: store the files in the database, store them on the server ... However, if you want to save them in a folder, take a look at this code that I used in the HTML5 file loader:

//Count files
$count = count($_FILES['file']['name']);
for($i = 0; $i < $count; $i++){
    //Path
    $filepath = 'upload/'.basename($_FILES['file']['name'][$i]);

    //Save file
    move_uploaded_file($_FILES['file']['tmp_name'][$i], $filepath);
}

, , .. : $_FILES['INPUT NAME HERE'][.....