Craft Query by Category and Tag
You'll probably want to read up a bit on relations in the Craft docs, but I think something like this should work

{# First get the category elements #}
{% set supportCategory = craft.categories().id(458).one() %}
{% set widgetCategory = craft.categories().id(459).one() %}

{# Now we use those elements in our query #}
{% set entries = craft.entries().section('Post').relatedTo(['and',
  { element: supportCategory },
  { element: widgetCategory }
]).all() %}

{% for entry in entries %}
  {# ... your code #}
{% endfor %}


I believe the relation needs an element, but you might be able to do something like .relatedTo(['and', 458, 459]).