Requests use the HTTP X-Api-Key header to both authenticate and authorize operations. API tokens are provided to you after you paid a HeyGen subscription.
As a developer, you'll need a pro HeyGen account first. Login you account and pay a pro subscription, then click the Account button at the left bottom, the API token shows there.
You can activate a trial token for testing on your account page. See below about how to activate your trial token:
KEEP TOKEN SECRET AND SAFE
Keep the API token secret and safe. Anyone with this API Key can use the HeyGen API as you. If it is compromised, please send an email to [email protected] and it can be deactivated or reset.