To change your font settings in Presspage Mail, choose 'Email' in the navigation bar on the top of the page.
Then, choose 'Settings' in the sidebar to the left:
You'll see three tabs. Choose the tab on the right, called 'Font settings'.
Here you'll be able to set font styling that will apply to all your email campaigns. For example, if your brand style guide says you're using Helvetica for headings, you'll be able to easily set that here. The first drop down menu lets you choose a font family for h1 thru h6 headings.
The second drop down menu lets you select the font size for the headings:
There's also a color picker to select the correct color and its hexadecimal value.
Of course, the way your main content in paragraphs look can be changed as well. Again, you'll be able to choose font family, font size and color. This also applies to table paragraphs.
Finally, you can change the appearance of hyperlinks. Keep in mind that links should easily be recognized as such, also to color-blind users. Generally, it's a good idea to keep links in your main content underlined.
Click the 'Save' button on the bottom right of the page when you're done.