Within Teamwork, you can quickly add a new event from any area of your site via the quick add menu.

Select + Quick add from Teamwork's main navigation menu. In the quick add pop-out menu, click ... More, then select Event.
 
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In the Add Event window, you'll need to enter an event name. You can also fill out details such as when, where, and attendees, as well as set reminders for the event. 

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For more information, see: Using the Quick Add Menu