dlm_pa_only_with_tags.php

function dlm_pa_only_with_tags( $args ) {

	$args['tax_query'][] = array(
		'taxonomy' => 'dlm_download_tag',
		'field'    => 'slug',
		'terms'    => array( 'tag1', 'tag2' )
	);

	return $args;
}

add_filter( 'dlm_page_addon_category_query_args', 'dlm_pa_only_with_tags' );