share wifi password on iphone x

My wife and I have iPhone Xs running. iOS 12.3.1

We also both have 2009 iMacs (vintage) and new iPad 9.7 " 6th generration

I understand that you are supposed to share wifi passwords between ip[hones. provided one of the iPhones is connected to the wifi service, and that both iPhones are near each other, and that you are on the other person's contact list. I tried that but nothing happens.

I also can't figure how to share wifi passwords with my iMac and my Ip[hone X.

Any advice? I tried following the online videos but it does not work.

Thank-you