How to use hook form alter to add to an existing form in Drupal 8

Modifying an existing form on a drupal 8 site

These are notes/documentation on how to change an existing form on a drupal 8 (D8) site so that you can add an element to it.  "[module]" needs to be replaced with the module name in the areas it is referenced in this document.

Create a D8 module

You need to create a drupal module with at least 2 files (with appropriate content for them to be an actual D8 module):

Creating a Drupal 8 Plugin to Handle State, City, and County Sales Tax

Steps taken to create a custom plugin for Drupal 8 (D8)

These are notes taken to document work (analysis, design, and implementation) to create a plugin to create a custom tax type for drupal commerce 2.0 that has the ability to use the SmartyStreetsAPI service plugin in order to lookup the county and apply sales tax appropriately for Colorado.