How to access the full html of a drupal basic page? This is probably a dumb question. But I have not been able to find the full html of a basic page. 
When I create a basic page, I can put a title and texts/images in the body. How can I access the &lt;head&gt;...&lt;/head&gt; portion of a specific basic page so that I can edit that part and put a js script? or better yet the full html of the page?

Thanks!
You will need to edit your themes tpl files to make changes to those areas.  If you are adding a js file you can add it in your themes template.php file. I would recommend you read through this link for

Drupal 7:

https://www.drupal.org/docs/7/theming

Drupal 8:

https://www.drupal.org/docs/8/theming