Thanks Glenn for the helpful information. I was able to locate the areas that I would like to change.
Below is one, with the text I want to enlarge to 1.6em in red. Sorry to be so dense, but I have no idea how to enter that into the code and exactly where.

[FONT=Times New Roman]define('HEADING_TITLE', 'Step 1 of 3 - Delivery Information');[/FONT]

[FONT=Times New Roman]define('TABLE_HEADING_SHIPPING_ADDRESS', 'Shipping Address');[/FONT]
[FONT=Times New Roman]define('TEXT_CHOOSE_SHIPPING_DESTINATION', ' Your order will be shipped to the address at left or you may change the shipping address by clicking the <em> Change Address</em> button.');[/FONT]
[FONT=Times New Roman]define('TITLE_SHIPPING_ADDRESS', 'Shipping Information:');[/FONT]