Consider going back to the Forms tab to create any new form steps required in your flow. Forms created in the Forms tab are reusable whereas forms created in the flow designer are not reusable.
The New Form palette control allows you to create a new form step in your workflow directly inside the flow designer. If you do not have an existing form for the step you require, drag & drop the New Form into your flow and create the step in place. This will launch the form designer where you can add controls to the form just as you would if you designed the form from the Forms Home page.
Drop the New Form from the palette into the flow. Click to select it. Then click the pencil icon to launch the form designer. A unique and arbitrary name will be generated automatically for the step--Form 29 for example. You'll change this name inside the form designer.
Consider going back to the Forms tab to edit the form. Then delete the old form from the flow designer canvas and add it back to the flow from the flow palette.
The palette contains all of the forms that you have already created and which are listed in your current application's forms home page. You can use any form as a step in the flow. Adding an existing form to the flow creates a copy of that form. If you later edit the form from the forms home page, those changes will not affect the step in the flow. It remains as it was at the time you copied it into the flow. If you want to update the flow to have a new copy of the form, delete the form from the flow and drag it in again. You can also edit the form directly in the flow. Conversely these changes to the form inside the flow do not affect the original form in the form home page.
Drag a Summary step anywhere in your flow. This will simply display a Summary view of all the data that has been entered into the various steps of the flow prior to the Summary step. The user can review the data and Continue or click on automatically generated Edit links in the Summary View to go back and edit the data.