Your Dashboard gives you quick access to your calendar, activities, and email, among other things. You access it by clicking on the drop-down menu at the top right corner of your screen, then clicking on Organizer Dashboard.
Your default home page will be your calendar, from which you can access your activity schedule, whether it's with a monthly, weekly, daily, or list view.
The Activities tab will give you access to all your activities to schedule and manage. They are organized as published, past or drafts activities.
The Messages tab allows you to access your internal messaging system, and thus to get in touch directly with the participants registered for your activities.
Finally, as its name suggests, the button at the top right is a shortcut to create an activity.