If you want to use the Tournament Registration feature you must turn it on. (You are asked if you want to use this when creating your event) If you said no at the time, you can still turn it on.
Turn on Tournament Registration
Menu > Manage > Tournament Registration > Manage User Registration
Click on Settings,
Check the Accept user registration (if you want players to be able to register for your tournament online, this puts them on a Waiting list until they pay you)
Check Accept online payments (if you want players to pay directly online, once the registration complete and the payment made, it adds them directly into your tournament)*
While you're in the Settings....
Take the time to go through the Validation Rules, Custom Values and User Messages.
Validation Rules : can help make sure sanctions are respected etc. (this only works for associations)
Custom Values : are fields you can add to the registration process if you want extra information. You can choose to make it mandatory or optional.
User Messages : These are messages you can modify, the automated messages appear in certain areas (specified in the user messages.
Create divisions you want players to register for.
Under Menu > Manage > Tournament Registration > Manage User Registration
Click on the Plus to add registration divisions.
This is where you will include all the details.