Change the height of the form

Could you please assist me how to resize the height of the form?
I only can find the width adjustment button in the 'preference - form
style' tabs.

There's no fixed height on every form. Form's height will automatically change according to the total length of your form fields.

If you want a fixed height in your form, inject the following CSS codes into your form.

.form-all{height:500px;}

Just change the 500px height to your preference.

Guide: http://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes