How to use costum field in the post

It is so easy. Just drag and drop any field (e.g: text, textarea, dropdown or whatever) in the post form and give it any name except the common names of post columns like ID, content. That’s it, this will be treated as custom field in the form. Any post created using that form will have the meta with the name of the field. And the value provided when creating the post will be the meta value of that custom field.
Thanks.