Where can I get Quick Calendar?
The Mac App Store.
How do I add the widget?
How do I add events?
Quick Calendar has no concept of events or reminders. It’s a simple, visual tool and not a full calendaring app.
How do I go to the next or previous month?
The little buttons to the left of the month and year are previous month, this month and next month respectively.
How can I ever thank you?
The main app has donation buttons. You don’t get any extra features but you do get my eternal thanks.
Can you add feature X?
By all means ask but I can’t promise anything. The only thing that’s currently on the roadmap is localisation and there’s no timeframe for that.