The EmailOctopus add-on needs to be installed and activated to see the features mentioned in this this documentation.

To create your EmailOctopus API key, login to your EmailOctopus Account then click on API from the left sidebar. Click on Create a Key and copy the API key.

Create EmailOctopus API key

Go to Ninja Forms > Settings > EmailOctopus and enter your API key.

Add API key to Ninja Forms settings

Go to Emails & Actions and click on the plus button in the bottom right and add the EmailOctopus Action

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.

Map the Ninja Forms fields to EmailOctopus

For information on how to setup your lists in EmailOctopus, please reference their support documentation.