To edit a form and add new fields, click on Actions -> Form fields and access the Edit Fields panel.
Here you can edit field text and add new form fields by clicking Add Field, where you have a number of field options to choose from (e.g., text input, password input, etc.).
By clicking on an existing field, you can change its title and layout and specify whether the field is Required (required to be filled in), Restricted (not visible to the reader and only fillable by admins) and Shown in List (removed from the list of entries).
A field can be deleted by clicking the corresponding Delete button.
You can change the location of fields by dragging and dropping them. To add a new page to the form, click the + icon at the top of the panel. If no content is added to the new page, it will be automatically removed when the dialog box closes.