How can I loop through a collection in the index file?
To set up a section (or check the one you are referring to), in your control panel, go to Settings then Sections.

To loop through entries on a template, for this service section for example, you do:

{% for entry in craft.entries.section('services').all() %}
    {{ entry.title }} &lt;br&gt;
{% endfor %}


Hope that helps :)