Hi James!
Thanks for reaching out to us! Let me help you with that.
The Community Events add form, as well as the My Events list, make use of the template selected under Events > Settings > Display tab and under Events template setting, you should be able to choose between the available templates.
If your theme provides a page template that has a sidebar, or any other custom template, you should be able to select it from there.
Our plugins provide the Default Events Template, which you can customize to suit your needs by following the Themer’s guide.
I hope that helps and let me know if you have other questions.
Best!
Victor