Settings for FirstSeed Calendar for Apple Watch can be found in FirstSeed Calendar for iPhone. Open FirstSeed Calendar on your iPhone, go to the Settings and tap "General" or "Calendars" under "Watch App" section. You can show or hide calendars in the Watch app, or change the information to be displayed in complications.
FirstSeed Calendar for Apple Watch supports displaying events and completing reminders. Other tasks, such as adding, editing, deleting events, reminders or calendars are not supported.