Preferences > Display > Formatting. You can set the default font and font size for the message display. The 'Advanced' button lets you set a minimum font size and override any settings within messages.

I hate to be stupid but how do I get to the "preferences" to enlarge my emai print size.

Are you concerned about print size, or display size on your monitor? If it's just the on-screen font, you can use the Ctrl-+, Ctrl--, and Ctrl-0 hotkeys to increase, decrease, and reset the display font temporarily.

Since you appear to be using Windows you would be looking for Options and not Preferences. Click the AppMenu button. 3 horizontal likes. Hover over Options and then click Options when that Menu appears.