Click on "Stories" in the app section. you can change the position of stories by dragging the app.

You can change the shape of the tiles to square or circle and adjust the corners, you can also customize the font and the padding separately for both mobile and web devices. You can change the primary theme color to something bright for reference, and as you can see, the colors have changed.

After customizing as per your needs, save the theme, to ensure your changes are not lost.