The method is the same as when inserting data into a contact list with an API, only the URL that calls the API changes.
1. Go to the tab "Extensions" to check that the API extension is activated.
2. Then, go to the "Blacklists" tab and you will see "Default blacklist". Click on the action API.
3. Next, a window will appear which contains some URLs. You need to copy the URL under "to insert a contact".
4. Then, follow the steps in our guide: Inserting data into a contact list with an API