Gizmo Hi, unfortunately you can‘t use those icons. There are part of the dashboard. Themes are something different and share no resources and dependencies with the dashboard for obvious reasons.
Using those icons in a template will break your site when running updates in the future. A template must ship all its dependencies itself to be future proof.
In order to use icons on a page it is the best to look for svg icons that can be embedded easily. Fortunately, there are many pages that provide free svg icons out there.