Standard usage scenario

1. Install the Metatag module.
2. Open the configuration at Configuration > Search > Metatag (/admin/config/search/metatag).
3. Adjust the configuration for global and entity defaults. Fill in reasonable default values for any of the meta tags that need to be customized. Tokens may be used to automatically assign values.
4. Additional bundle defaults may be added by clicking on the "Add default meta tags" button and filling out the form.

If you want to allow users (eg editors) the ability to change/override an individual node/entity metadata via the form, add a meta tag field to the content type by following these steps:

1. Go to the "Manage fields" of the entity type.
2. Select "Meta tags" from the "Add a new field" selector.
3. Fill in a label for the field, e.g. "Meta tags", and set an appropriate machine name, e.g. "meta_tags".
4. Click the "Save and continue" button.
5. If the site supports multiple languages, and translations have been enabled for this entity, select "Users may translate this field" to use Drupal's translation system.