Use this code to organize all file uploads by username within the parent form ID folder.

add_filter( 'frm_upload_folder', 'frm_custom_upload', 10, 2 );
function frm_custom_upload( $folder, $atts ) {
    if ( $atts['form_id'] == 25 ) { // change to your form id
        global $current_user;
        $folder = $folder . '/' . $current_user->user_login;
    }
    return $folder;
}

If you are using a caching plugin setup with a CDN, it will work best if you leave the uploads in the regular uploads folder.

add_filter('frm_upload_folder', 'frm_custom_upload');
function frm_custom_upload($folder){
    $folder = '';
    return $folder;
}

If you would like to set a custom path for your file uploads, this example should be a good starting point.

add_filter('frm_upload_folder', 'frm_custom_upload');
function frm_custom_upload($folder){
	$folder = '../../wp-content/uploads/product_images/';
    return $folder;
}