When creating a new Lead Capture form you can choose to send submissions directly to your ActiveCampaign account.
Step 1 - Add A New Provider
Under the integrations tab select 'providers' and click the 'add a new provider button'
Step 2 - Connect To ActiveCampaign
Enter your API URL and API Key as shown below. For details on how to find your API settings please read this article.
Step 3 - Select Your List
When someone opts-in to your form their details will be added to an ActiveCampaign list of your choice.