You can retrieve your production and sandbox API keys from the API keys page.

All requests must be made over HTTPS and will be authenticated over standard OAuth authentication. When providing credentials, the username will be your Client ID and the password will be your Client Secret.

API keys must be kept secret. They should not be in your client-side code or checked into your application's code.

Sandbox

curl -u <api_key>:<api_secret> \
  -XPOST https://auth-sandbox.swifterhq.com/oauth2/token \
  -F grant_type=client_credentials

Live

curl -u <api_key>:<api_secret> \
  -XPOST https://auth.swifterhq.com/oauth2/token \
  -F grant_type=client_credentials

Use the access_token as the bearer token in the subsequent API calls, by setting in the Authorization header.