Under the Systems tab, you enter the access data and other information for the integrated systems. Which data you have to enter always depends on the connected system. As a rule, the following information must be provided as a minimum:
The endpoint or module is often selected in a previous step (see screenshots). If a custom module is to be synchronized, then the name must be entered in a free text field.
The screenshots show that depending on the system and the selected endpoint, a wide variety of information is required.
You should definitely create a separate API user and not use the credentials of your regular user account of the systems!