Calling Web API from an external system

I am trying to access Appian data from an external system. If I send a 'GET' request on the URL of the webapi with the appropriate endpoint, I run into Cross Origin Resource Sharing problems and the headers provided do not pass my pre-flight request. I wanted to know if there are any configuration changes in Appian's webAPI needed to do so that it responds to requests sent from the other system's URL ?