Hi on this page I have a form and some other information and I am not sure how to change the font size.

http://www.thebrumbyshop.com/contact-us/

Also how would I make the message box wider?

And If its not too much how do you make those boxes around the form I tried to make one around the table with a border and set the size to 1 but does not look right not important but would like to no.

You can do all of this with CSS, just read up on that a bit, its not really related to silverstripe. You shouldn't be adding borders onto the table, thats how it was done 10 years ago. I'd suggest giving your table an id such as <table id="contactinfo" cellpadding="0" cellspacing="0" border="0">

and then in your css file:

#contatinfo {
border: 1px solid black;
}
#contactinfo td {
padding: 5px;
}

css styling forms to change the font-size/box widths/whatever is much the same.
For silverstripe forms in particular I'd start your form.css (yours looks empty at the moment?) file with the code from:
http://doc.silverstripe.org/doku.php?id=amazing_looking_forms_using_silverstripe_form_default_rendering&s=amazing%20form

and edit that until it looks how you want