How to get API key and Listing ID.
Please follow the steps below:
Click to account section in the header and click to menu "Account"
Then choose Settings > API Keys to go to the API page
On the API pages, you choose Create API Key
When you completely created, you need to copy that key
To find the list ID for an existing Klaviyo list, navigate to the Lists & Segments tab of your account and click on a particular list.
Then, navigate to the Settings tab in your account. Here, you can find a list's ID. Every list has a unique ID, as does every user, flow, campaign, etc.
Additionally, you can find a list's ID in the URL in your browser when viewing this list. In the URL, you will find a short series of numbers and letters -- this is the list ID.
Example for new Klaviyo profile