The integration API uses basic authentication. Basic authentication is a simple authentication scheme built into the HTTP protocol. The client sends HTTP requests with the Authorization header that contains the word Basic followed by a space and a base64-encoded string username:password.

For example, to authorize as demo / p@55w0rd the client would send:
Authorization: Basic ZGVtbzpwQDU1dzByZA==

This site can be used to generate the header value: