WordPress: Where to add code unregister specific taxonomy for post

There is an answered question How do I remove a taxonomy from Wordpress?. The last answer suggests adding specific code:

Blockquote

Perhaps a more technically correct method would be to use unregister_taxonomy_for_object_type

enter code hereadd_action( 'init', 'unregister_tags' );

function unregister_tags() { unregister_taxonomy_for_object_type( 'post_tag', 'post' ); }enter code here

Blockquote

I assume I only need this code to run once. Where do I add the code and how to adjust it to remove tag health-area

via Chebli Mohamed