Hi Sharon,
Thanks for getting in touch!
The calendar unfortunately does not include a sidebar in the event template. However you can change the template to one of your theme’s templates that has an existing sidebar under Events > Settings > Display. That would give you a sidebar, but it would be controlled in the Appearance > Widgets area rather than be a unique sidebar to a specific event.
The other thing you could do is add a new sidebar directly to the event template. We’re fairly limited in how much support we can provide for custom development like this, but do have a Themer’s Guide to help you get started and I’d be happy to answer any specific questions you have as best I can.
Cheers!
Geoff