So I was wondering if there is a blog or article about adding a new template to a siteand then the best steps to get it to to look like the template preview or use it to its best effect with our own content.
Hi. Simple steps - install Helix and set it as default template, configure the appearance through available interface settings.
If this is not enough for you, then use your browser's dev tools to determine the necessary HTML selectors, use custom CSS coding by adding your code to the custom.css file to bring your site to any appearance that you want.
Therefore, a blog or article in your case will be (if you do not have CSS skills) the studing of HTML/CSS, for example using https://www.w3schools.com/, the reading Helix documentation and the studing Helix's code structure via dev tools.
Or hire someone for this work.
All this applies to any template in the market, but not only to Helix. You can use any template, as it is, with the default styles from the box. Or you can make any appearance through CSS coding.