The form-builder doesn't have a direct option to show the question titles and description in the centre of the form, but there is a simple method which will bring you the desired look.
Different form looks: Left: Left-aligned text; On the right: Centralized text elements
Check this video for the full explanation of how to move your form elements to centre. Read on for the explanation in this article:
To bring question title and description text to the centre, you need to add textbox and move it above your question.
First, simply click on the orange button below your question.
Then click on "Textbox" to add a textbox
In the textbox simply type in your question title and description text as needed and use the editor to make changes to size, formatting and alignment
Next, make sure to hide your title and remove any text from the question description so that your textbox title and normal title and description text doesn't appear twice.
Follow the same steps for your next questions to centralize your title and description elements across the whole form.