You can use the Customise feature of the store’s Theme panel to move around text, graphics, videos, adjust columns or adjust elements in pages. The editor is a Live theme builder so you can change the fonts and colours of pages and see the results as you change them. You can make changes just for a particular page, or for the whole site.
For advanced users, if you are experienced with CSS Stylesheets you can also add custom CSS for the page or site to override the built-in design elements.