how to keep Athena settings when enabling a child theme?

I’m trying to set up a child theme just to add a bit of css. When I activate the child theme, I lose the Athena settings. I see no instructions in any of your documentation for setting up a child theme. I’ve done this many times before and have never had this problem. Can you please advise? I’d really appreciate it.

This is for a not-for-profit on a very strict budget. Upgrading is not a desirable option.