I have created a custom post and fields. Now I need to create these posts via an automation. I need some help/direction in creating posts through php code. I can use WordPress function to create posts but I need some guidance on adding field data and taxonomy to the posts via code.
To save custom fields, you would use update_post_meta (https://developer.wordpress.org/reference/functions/update_post_meta/). The one thing that you need to be aware of here is that if you have set up custom fields with Types, then the corresponding meta key has a 'wpcf-' prefix, so a 'priority' custom field would have a key of 'wpcf-priority'.
For taxonomies I assume you already created the custom taxonomies and terms, and will be programmatically assigning them. For that there are a number of functions you could use, with wp_set_post_terms your best starting point: https://developer.wordpress.org/reference/functions/wp_set_post_terms/