The author of this template achieved this effect using an image of the arrow. If you want to re-create it (but want a different color arrow), you could take a copy of that image and change it using (on a mac) the preview app or (don't laugh at me) powerpoint if you don't have access to image editing software.
we're working on continually improving template content so the templates are more approachable.
Here's the code for that one in case you missed it.
```
<h5 class="primary-color text-right">Learn More
<a href="https://community.esri.com/pages/contributing-factors" role="button">
<img style="height: 100px;" src="https://arcgishub.maps.arcgis.com/sharing/rest/content/items/440da588ba764fd896fa1c5da8c244ea/data">
</a>
</h5>
```