Steps for Appian to External System

We need a lot more information to be able to help you. Are you trying to set up an integration where Appian makes a request to an external system or where an external system makes a request to Appian? What kind of system / protocol are you integrating with? What kind of information are you sharing to / from the external system?

I'd also recommend looking at the documentation for Integrations - it's pretty comprehensive and should be able to answer a lot of your basic questions.