There are a few different types of component which should be used in different ways.
Block-type components use wagtail blocks for use in a streamfield.
example: ActionLink
Templatetag-type components can be included in templates with django templatetags.
example: Breadcrumb
Template includes can be used with the {% include %} tag in your templates.
example: Header (via templates)
Wagtail site settings must be enabled with the wagtailnhsukfrontend.settings app.
example: Header (via settings)