Allow shop manager to use revolution slider

Which attribute shall I insert to this function in order to allow the shop manager to use the revolution slider plugin? I tried this but it doesn't work!

function add_theme_caps() {
    $role = get_role( 'shop_manager' );
    $role->add_cap( 'edit_rev_slider' ); 

}
add_action( 'admin_init', 'add_theme_caps');

Thank you in advanced!

via Chebli Mohamed