To customize your store's appearance, you have two options:

1)  Basic settings page : Here you can change the store name, the number of items to display per page, add a header and footer image, a title and description for the store, and several other configuration options.

2)  Colors and background : Here you can change the store's font, the colors of all the font types (titles, main and secondary text, buttons, links, etc.), as well as the background colors (outer and inner background, menu, separator lines, etc.). You can even set a background image.

It's best to make the changes you like and refresh your store's page as you go to see how it looks until everything is to your liking.