I'm looking for a starting point on how to POST a subscriber to a list so that they are able to opt-in to a list from which I grab from Marketing Cloud. I am using SSJS to grab all of the lists that I need from my instance, but now it's at the point where I need to offer these lists to people so that they are able to opt-in or out of these lists.
I imagine this will require SOAP API, which I am very basic to and was looking for a little starting point as to where to start with the API. Or does it require AMPscript instead?
Also, will I have to change the way that I grab the lists? I am just pulling them using SSJS and displaying them on a landing page. I imagine I will have to change this by the sounds of it.