how to impliment gtags in Dreamweaver CS6 version 12

The official answer from Google Developers (Add gtag.js to your site  |  Analytics for Web (gtag.js)  |  Google Developers)

Install the global tracking snippet

To install the global tracking snippet, copy the following code and paste it immediately after the <head> tag on every page of your site. Replace GA_TRACKING_ID with the tracking ID of the Google Analytics property to which you want to send data. You need only one global snippet per page.

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=GA_TRACKING_ID"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', 'GA_TRACKING_ID');
</script>

This snippet loads the gtag.js library, establishes GA_TRACKING_ID as the default Google Analytics property ID, and sends a pageview hit to Google Analytics.

If you'd like an easier way to track any Google and other 3rd party Javascript plugin and tracking codes, I highly recommend using Google Tag Manager (https://tagmanager.google.com) along with both the Google Page Analytics (1) and Google Tag Assistant (2) Extensions for Chrome. All three together will make tagging and tracking much easier to handle.

Personally, I find tracking evil.  But..

According to https://developers.google.com/analytics/devguides/collection/gtagjs/, you place the code after the <head> tag.  If you are not using a header file, then it goes on every page.  If you are using a header file, then it goes just in the header.

HTH,

^ _ ^