How can I resize my form page?

You could use this CSS and copy in your Custom CSS field:

.form-all{

   width:200px!important;

   height200px!important;

}

And just adjust the values for width and height at your preference.

Here's a guide How to Inject Custom CSS Codes.

If you were looking for something different, please let us know so we could check for possible options.

Thank you.