Your drop down theme selector allows you to offer more than one style on your website, for your visitors to choose from. It only appears when there's more than one theme present, and it can be switched on and off at Admin Panel -> Settings -> Switches -> "Theme selector". If the theme selector is switched off that means unregistered guests will be stuck with the default theme, but registered members can still change the theme by editing their profile.

Offering a variety of themes allows you to please the differing individual tastes of your website's visitors. This customization can make them more loyal.

To install free pre-made themes go to Admin -> Themes -> Add Themes. To add your own style or make changes to a style see Creating a New Style for more information.

To change the default theme, go to Admin Panel -> Themes -> Theme Settings.