Final answer:
The theme ID needed to connect Theme Kit to a local Shopify theme can be found in the Shopify Admin under Online Store > Themes. It appears in the URL when editing the theme's code.
Step-by-step explanation:
To connect Theme Kit to your local theme on Shopify, you need to specify a theme ID. This ID can be located by going to the Shopify Admin area, navigating to Online Store and then to Themes. Your theme's ID can be found in the URL when you click on the theme you want to work on, or by clicking on the theme's Edit code option where the URL will contain the theme ID at the end.