(1) Open your Klaviyo account and navigate to settings > Account > API keys > Create Private API Key
NOTE: PLEASE ENSURE YOU CREATE A FULL-ACCESS API KEY
(2) Copy this API Key and fill it in the app’s Email service provider section. Navigate to settings > Integrations > Email Service Provider. Select Integration as Klaviyo and fill up your Klaviyo Private API Key and save it. 
NOTE: Only one email service provider can be Integrated at a time
