On the "Details" page within your event, you will see "Components" listed at the bottom of the page. To add a component, there will be an option in blue that says "+ Add Component." Click that link and follow instructions.
To edit a component, click the arrow in the bottom right of the corresponding box. That will open the component and take you through all of the necessary steps to edit it.
For both steps, make sure to click "Save" at the bottom of each screen.