In the walkthrough editor, under Advanced Properties, one of the configuration options is Advance When Target Clicked.
The Target is defined as the Target Element configured in the Core Properties section and refers to the element on the page the walkthrough bubble points to.
Instead of using a Next button to advance the walkthrough, you can have the help item advance when the target element is clicked. To configure this action, go to the Advance Properties section of the walkthrough builder and click the Advance When Target Clicked toggle to Yes.