Hi Jessica!

Please go to "Style Customizer > Others > Custom CSS" and try this:

@media only screen and (max-width: 767px) {
    #content-container .columns, #content-container p {
        font-size: 10px;
    }   
}

This would make the font size 10px for ".columns" and "p" selectors when viewing on the resolution belower than 767px.

In case you want to adjust other elements on various resolutions, I would recommend this:

1. http://responsivepx.com/ for simulating the viewport.

2. Use "Developer Tools" on Chrome or "Firebug" on Firefox to inspect the elements you want to adjust.

3. Use the proper CSS media queries to set the CSS for specific resolutions. Note that you can google for more info about CSS media queries.

Regards,
Paul