Welcome to pg-discuss!
To embed the widget into an HTML page, you need to add a script tag:
<script data-isso="{{ request.url_root }}" src="{{ url_for('static', filename='embed.min.js', _external=True) }}"></script>
and a section tag where you want the comment widget to be rendered:
<section data-isso-id="my-thread" id="isso-thread"></section>
Replace "my-thread" with a permanent, unique name for the article/page you are embedding the widget into, such as a UUID or the article slug. If you are using a templating system that cannot generate a unique name, you may omit the "data-isso-id" attribute entirely, and the URI will be used as a thread identifier.
For more configuration options, see the Configuration docs.
Here's an example with a "test" thread: