In your Mailjet account, open the "API keys" page. We'll reuse the details at step 5.
Log in to your WisePops account.
Open your popup in the editor and click on the email form:
In the left panel, click on the "Mailjet" icon
In the popup window that opens, enter your API credentials and click "Submit"
Select your destination list
If you've added extra fields, make sure to merge them:
And voila, you're done.