Follow these set of images to connect via api to your activecampaign.. To know how to create a webform and add that into easywebinar then please scroll down to watch the video..
Log into your AC Account
Add details here
Then when you create an event you can select your autoresponder here as well as select the list to add names to and the tags.
In the video below it will show how to create the custom form and add the code if you want to use it intead.. The image is where to add the form code and you get the thank you page url in publishing options instead of actions tab..