How do you get back the bigger dialog box in a form online?

Accidentally I clicked on something which made the dialog box for the “message” smaller. Now I can’t print it, (my message) or take a screenshot of it, without missing part of it. So, how do I get back the big size back? There is no “cc me” box that is why I need to print it.
(Added: I was trying to send an email they only have a form to fill out for that.)