The API uses Bearer token authentication. Include your API key in the Authorization header: 
Authorization: Bearer YOUR_API_KEY
The Daydream API is currently in closed beta. To request access, please fill out this form, and the Daydream team will be in touch within 48 hours.In the meantime, we invite you to join the conversation and meet fellow builders in the Daydream Discord server.If you already have access to the Daydream beta, you can generate your API key here -> Beta API Key