Your mobile editor will allow you to change the size of any elements and the layout of the elements on the page.
You can access these setting once you have change to the mobile viewer, the mobile viewer is located on the Top main menu bar. (At the top of the editor)
Once you are in the Mobile view, the options on the Left side tool bar will change. These are settings that will allow you to make changes to the size and layout of your mobile site or by actually selecting the element on the page.
For example: if you click on any text that you would like to change the style of, you will have an option to switch on editing from the pop-up menu that will appear to the right of the screen.