For the authentication, we use basic http authentication. This means you have to set the Authorization tag/property for each request in the header.

The value of the Authorization has the following format: “Basic” followed by space and a Base64 encoded string which has this input format: “username:password@domain”.

The user should be flagged as 'Allow throught API'.

E.g. using the credentials below:
Domain : TESTAPI
Username : APIUser
Password : 123456

The input for the Base64 encoded string would be APIUser:123456@TESTAPI

The resulting Base64 encoded string:

QVBJVXNlcjoxMjM0NTZAVEVTVEFQSQ==

And the Authorization tag:

Basic QVBJVXNlcjoxMjM0NTZAVEVTVEFQSQ==

Authorization: Basic QVBJVXNlcjoxMjM0NTZAVEVTVEFQSQ==

Note: OAuth is not possible for the moment.