To get authorized into an account, there are at least three elements you need; the institution, the username, and the password. With these elements, you can be directly authorized through the bank by the authorize endpoint.
Careful, if you don't put the parameter 'save' your data won't be saved in the database. This means you won't get any Transaction Ids and you won't be able to make a cached call. See an example in the image below
You may also receive a 203 code. In this case, you need to answer the MFA challenge before successfully authorizing. With the authorize endpoint again, answer it correctly to receive the StatusCode 200 and complete the authorize part.
Finally, you can get authorized with the Login Id and also in cached mode. Those 2 don't need to go together but are often use like this
To know how to get your Login Id click here.
When you get a StatusCode 200 that means you are now authorize into the bank and you may use the Request Id to call any other endpoint to retrieve datas.