From the Forms dashboard, you can edit any one of your Forms. Click on the grey hamburger icon to the far right hand side of the Form you wish to edit.

From here, click the "Edit" pencil icon within the drop down menu. Here, you can edit the title of the Form, the Form description, who the Form is visible to, and every other aspect of the Form you created.

To edit a specific section, click on the grey pencil icon to the right of the section you wish to edit. From here, you can update, delete and/or add new fields/questions to each section.