Manage your Apple Card account
https://support.apple.com/kb/HT209228
I don't know how linked an Apple Card is to a specific account and if you'll basically have to set up a shared account with yourself.
Set up Apple Card Family and add a co-owner and participants --> https://support.apple.com/HT212020
You may need to get Apple to answer your question about this.
If you still have problems:
Contact Apple. Click here --> https://support.apple.com/choose-country-region Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world."
Click here --> https://support.apple.com/HT201232