Go to Manage events and choose the series on which you wish to create a new event in the drop down box. If the series is not there then ask your events manager to grant you administrator rights. If the Manage events menu option is not there it means you do not administrate or organise any events; if this is the case please refer back to you events manager for access.
Having selected the series, select the New tab and enter the start and end dates for the event. If the event is a sporting one (say a tennis tournament) then these dates represent when play is expected to start and end - the end date typically being the finals day. If the event is a social event, for example, a club dinner, then put the date of the dinner in both start and end slots.
Then hit the Add button and a new event will be created and put into the "pending" stage.
You will have been assigned the organiser of this event and there are event organiser articles to help you.