Here’s a help article that also talks about billing and the auto-recharge.
https://help.openai.com/en/articles/8264644-what-is-prepaid-billing
If it is not accurate in its walkthrough, you can make your own screenshots here to show what a new user is seeing when they buy their first credits, and the buttons you can then choose to arrive at auto-recharge options in your billing overview.
I saw a Reddit post where some else also couldn’t discover the auto-recharge option.
PS I also just got hit with the “action required” email about being switched in a week.