Integrating with Ninja Forms - Create opt-in forms for Wordpress
Go to Ninja Forms > Settings > EmailOctopus and enter your API key.
Go to Emails & Actions and click on the plus button in the bottom right and add the EmailOctopus Action
Select the appropriate list from EmailOctopus then add the Merge Tags to map the Ninja Forms fields to the appropriate EmailOctopus fields.
Click here to view the Ninja Forms documentation page.