To add more distances or modalities (cycling, triathlon, etc.) to your event go to your events and click on Edit mmm yyyy Edition button.
Next scroll down to "Races" section.
You can either add a new race from scratch by clicking on the + Add a race button or you can use one of your existing races as a base. To do that, click on Copy <race name> button. This will create a copy of that race. It helps when creating additional races if they have similar characteristics.