Changing font size for .editor-preview

[2arch]

How do I edit the font size of the text once I toggle the preview button?

.editor-preview, .editor-preview-side { padding: 10px; background: #ffffff; font-family: Arial, Helvetica, sans-serif; font-size: 15px; overflow: auto; display: none; box-sizing: border-box }

I've tried editing the simplemde.css file and I've also included a snippet in the html itself referencing editor-preview, however have not seen any progress.

Changing the font-family to Arial, Helvetica works in the code above.

However, changing the font size of the rendered text doesn't seem to be working as intended. What do I need to edit for this to work properly?