Klaviyo

Step 1: Go to your Account.

Step 2: Click on Settings and select API keys on the menu bar

Step 3: View both your public API key (i.e., Site ID) and your private API keys in this location

If you don’t have an API Key, click on “Create a Private API Key”.

More info:

https://help.klaviyo.com/hc/en-us/articles/115005062267-How-to-Manage-Your-Account-s-API-Keys