I need to show a warning only if the customer has chosen that he will get to the place by car. How to configure this?

Open the resource configuration. Add a Reaction.

Enter a name. Select the reaction type — Show warning. Enter the warning message text and click Add condition.

In the list, select the field "By car" with the Checkbox is checked condition. The warning will be shown when the customer selects the By car checkbox. Save your changes.

The warning message is displayed with an orange line. It appears both when selecting options and on the cart screen.

Here is the result: