register_taxonomy() function into our functions.php file.
Just open your functions.php file.
And paste the below code at the end of your file.
add_action( 'init', 'create_events_taxonomy' );
function create_events_taxonomy() {
register_taxonomy(
'events',
'post',
array(
'label' => 'Events', //events are our taxonomy name, you can add yours.
'hierarchical' => true,
)
);
}