Klaviyo

In Klaviyo, click your organization name in the lower left → Account & billing → Settings → API Keys → Copy your public API key.

You will also need to create a Private API Key with read permissions to Accounts, and read/write permissions to Profiles, Lists, and Events.

In Polytomic, go to Connections → Add Connection → Klaviyo.

Enter your Klaviyo Public API Key and Private API Key