Simply create an account and login to your dashboard to view your API key.
There is no credit card or payment required to get an API key and use any of the BigDataCloud APIs.
Please note that it can take up to 15 minutes for the newly created key to be available for use worldwide. This is due to the need for API propagation, which requires some time to update the API key across all servers. Hence, if you get an error when using a new API key, please wait about 15 minutes before testing it again.