You must navigate to Settings » General first. Add wpf-center to the Form CSS Class box.
Now, Navigate to Appearance >>> customize >>> Advance CSS
And finally, we now just need to add the CSS to our site that will center a form.
add below mentioned code as it is.
.wpf-center .wpforms-submit-container { display: inline-block; text-align: center; width: 100% !important; }Booom.