For Shopbase site

Click the account dropdown in the upper right-hand corner of your screen > Select Account > Arrive at the Account Overview page > head to Settings > select API keys.

Copy Public API Key of your account as the image above.

From your ShopBase admin, navigate to Marketing & Sales > Marketing emails > select Klaviyo.

Paste the Klaviyo API Key you copied earlier to Public API Key in Klaviyo Tracking section.

Click Save.

For detailed information, read here.