How can I call an external API from Airtable to CRUD Airtable field ? Is there any tutorial available?
You cannot call any API from Airtable. Instead, you need to do it from your code (php, js, java etc.) to obtain the data you need then use Airtable API to CRUD Airtable rows/fields as needed.
Check out the API at https://airtable.com/api. Some basic tutorials are covered there.