There are two ways of authenticating with the API. Via an API key (tied to a project) or via the username / password of a user. For most programmatic access we suggest you use API keys.
Authenticating through API keys
Set the x-api-key HTTP header to an API key. An API key looks like: ei_a82b... and can be obtained from the studio.
Authenticating through username / password
First, obtain a JWT token via the 'Get JWT token' API. Then set the jwt cookie for subsequent requests.