The ConvertKit add-on needs to be installed and activated to see the features mentioned in this this documentation.
Connect to your ConvertKit Account to Ninja Forms
Then go to Ninja Forms > Settings > ConvertKit and past in your API key.
Send your Form Data to ConvertKit
Go to Ninja Forms -> All Forms and edit one of your Forms. On the tab Emails & Actions you’ll see a + on the bottom right to add additional actions.
CONFIGURE THE ConvertKit ACTION
Subscriber Email – This Field is required by ConvertKit to save the data in their system. You will want to connect this field to an Email field on your form so users can enter their email address.
Form – This allows you to choose the ConvertKit form you would like the user’s information added to.
Sequence – The ConvertKit Sequence is the sequence that you would like ConvertKit to execute when the submission is made. http://help.convertkit.com/article/10-convertkit-sequences
Tags – Tags in ConvertKit are further ways to segment and identify users in ConvertKit. http://help.convertkit.com/article/12-convertkit-subscribers#f4
Fields – Under the Fields section, you can associate form submission data with additional ConvertKit information.
Advanced – You can turn on debugging to see that data that is being sent to ConvertKit trough the API.