The easiest way to set up an event, is to copy a similar event, such as the previous year's conference. If this is the first time you are running such an event, or the previous event(s) were substantially different, then you will have to set up a new event from scratch.
In the Registration module, find the previous event, and select the copy tool. You can update the event name, and provide a new starting date. All dates in the event (including activity schedules, and fee close/open dates) will be advanced accordingly. You can then edit the new event to fine-tune the new event schedule, add and remove activities, update your fees, revise your notifications, and so on.
Note that the copied event has the same workflow status as the source event, so your new event may be fully enabled and open for registration. You will probably want to keep it under wraps while you reconfigure it, so the first thing you should do is configure the event, and set its status to draft so that the system knows it is not ready for prime-time. It should be sufficient to do this for the main event only; you don't need to set the status for every activity and fee.
Later, when setup is complete, you can publish the event, will will activate your changes and allow the public to register.
If building a new event from scratch, start with the Calendar module, and create your new event. At a minimum, you will need to give it an event name and a start date. If the event spans multiple days, you can provide an end date. Times are helpful for short events of a few hours or less, but for full-day and multi-day events, you can ignore the times.
The event description can be filled in later if you don't have that information at this time.
If event set-up is expected to take some time, it is a good idea to configure the main event and set its status to draft to keep it off the public event calendar while you work.
If your event includes activities (sub-events) that require separate registration/confirmation, you will also need to add those: use the + new activity tool and add the activity the same way you added the main event.
You may also want to add an event location, using the location tool. This will allow you to include venue information and a map in your event details. It also provides information to the e-commerce system about where the event is located, in the event that taxes need to be charged based on the event locale instead of the seller or buyer's location.
After your activities have all been prepared, you can move on to Registration Setup.