(2) Add a Page

Select a layout you want to use for the page. By clicking the icon, you can start creating a page.
You can create up to 20 pages.

The Summary Page (Salesforce Layout) is intended to be used as a last page in a wizard, for showing all the input fields exist in the wizard for the final confirmation for the user.
Therefore, the summary page cannot be created if you have not started creating a page.
When creating a summary page, all the input fields are automatically converted into reference fields.