Once a droplet has been created, simply drag items in the Finder to the droplet to perform the action the droplet was created to do. You can also add droplets to the List window's Open In menu to apply their actions to selected items in List windows.
Droplets do no processing themselves. Instead, they pass items on to File Buddy to do all processing. Thus you can redistribute droplets to other File Buddy users, but if File Buddy isn't installed they will only display an error message when used.
When using AppleScript to invoke a droplet, the droplet will not quit after processing the items. Add a line to the end of the AppleScript telling the droplet to quit to address this.