If site is down, how do I

What was the error message?

cannot remember and we didn’t take a screen shot. I do remember something about it being a “parse error”

Try checking your site’s error logs for a more specific error message. Your hosts should be able to help you accessing your site’s error logs. Once we know the error, we may be able to help you get the site back up again.

We made a backup but how do you access the backup if you can’t get into the admin panel to restore the backup?

You can either make a fresh WP install, install UpdraftPlus, upload the backup, and restore it (make sure that you have a copy of the backup saved elsewhere before you remove the existing install, of course), or you can restore manually via this guide:
https://updraftplus.com/faqs/i-want-to-restore-but-have-either-cannot-or-have-failed-to-do-so-from-the-wp-admin-console/

David