SlidePress allows you to backup and/or share your style presets with other SlidePress users. This is handled by exporting style presets to a static XML file. These instructions will explain how.
Click on the "Manage Gallery" link in the SlidePress plugin box in the left column of the WordPress control panel. This will take you to the "Manage SlidePress Galleries" screen. Click the "edit settings" link next to the gallery you wish to export presets from.
Scroll to the bottom of the page and you'll see an "Export SlidePress Settings" box. The input field will be pre-filled with the style's name, which you can change if you'd like. Click the "Export" button next to it, and the XML file will be downloaded to whichever local directory you have configured for downloads in your web browser.
Open your FTP client and connect to the domain where WordPress is installed. Navigate to the /wp-content/uploads/slidepress/templates directory.
Take an exported XML file and upload it to the directory above.
Open your web browser, and navigate to the SlidePress plugin area of your WordPress install. You should now see your uploaded style in the "Optional Style Preset" drop-down.