If you want to change the size of your form, open the Form Layout panel at page top in your Form Editor and change the Form Width. By default, the form’s width is set to 650 (pixels). The form height depends on the form fields. If you want to make the form larger in height, then place field labels on top of fields (Form Layout → Label Placement → Top Aligned). If you want the form height to be smaller, then align field labels to the left or to the right (Form Layout → Label Placement → Left/Right Aligned).