Change fields height and width

Dear Sirs
I need to change the width and the height of my contact form 7 text fields and send button.
I have read about other post in this forum but sorry I can’t work out where the changes need to be made.

In this following URL
http://marionstone.com/new/contactform7/
I have added for you to view the example of how is the current design and what I aim achieve. I

Please can you help me?
Thank you!

https://wordpress.org/plugins/contact-form-7/