The registration opening tab is where you can set the date and time that the page will open to the public.
Until the date that you set, the page is not available for use and a message that you have entered into the 'Registrations not open display text' is shown on screen - in this case it would be: 'Registrations are not open yet.'
At the set date and time that you have set for registrations to open the page will automatically open.
Alternatively you do not have to select a registration opening date. If you choose not to set a date, the registration page will be open from when your event is approved.