The development environment URL for the API is https://development.knotapi.com and the production environment URL is https://production.knotapi.com. Authentication to the API is performed via HTTP basic authentication. Requests made over plain HTTP or without authentication will fail. Your API key is the base64-encoded string username:password. In the Knot Dashboard, you will find your client_id and secret for the development environment, which you can use as the basic auth username and password respectively to generate your development API key. When you are ready to go to production, use your production client_id and generated secret (found in the Knot Dashboard) for your production API key. 
# Create a session with your development client_id and secret
curl -X POST 'https://development.knotapi.com/session/create' \
-u '[client_id]:[secret]' \
-H 'Content-Type: application/json' \
-H 'Knot-Version: 2.0'