Add custom caterogy/tax

Is it possible to add custom taxonimies to plugin? It has now category but I would like to add one more custom taxonomy. I tried to add usualy way but it didnt work.

function people_init() {
	// create a new taxonomy
	register_taxonomy(
		'team-member',
		array(
			'label' => __( 'People' ),
			'rewrite' => array( 'slug' => 'person' ),
			'capabilities' => array(
				'assign_terms' => 'edit_guides',
				'edit_terms' => 'publish_guides'
			)
		)
	);
}
add_action( 'init', 'people_init' );

Like that but didnt show up. Any suggestions what im doing wrong here?

https://wordpress.org/plugins/our-team-by-woothemes/