In the tutorial I am following, it menchens event sheets, and how there should already be an "event sheet tab." I don't have an event sheet tab. How do I add one?
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Official manual: https://www.scirra.com/manual/121/event-sheets
I will just answer your question...
By default, to the right of the main window look for the projects panel. Now look for the folder where it stores the events "events folder". Right click on it and choose to add event sheet.