Hello @Shaman22,
Thanks for writing to us.
For the sidebar, you need to create a new sidebar where you can add your widgets that you want to show and then assign it to that page. Please have a look at our doc to learn more how to add a custom sidebar and how to assign it to the page.
https://theme.co/docs/work-with-unlimited-sidebars
To align the content box centre, it not possible to provide a proper solution without checking the exact page URL or any screenshot. I would request you to share an exact page URL or marking screenshot.
Thanks