By default, Send to ScreenToss appears as a system service, available in any application that supports them, including the Finder, most web browsers, and most applications where you can select text or drag images. You can right-click on files, pictures, and selected text to share them with ScreenToss, or use the Services menu (which is always available in the Apple menu).
To add a custom keyboard shortcut, or to disable the service, open System Preferences ▸ Keyboard ▸ Keyboard Shortcuts ▸ Services. To set a keyboard shortcut, double-click the right-hand side of the Send to ScreenToss item and enter a key combination when the field appears to be editable. To disable the service entirely, uncheck the box to the left of Send to ScreenToss.