put my wifes email addres on my macx

Open system preferences > iCloud in the window again click on iCloud , and fill up the iCloud mail address that your wife previously created .

See the article https://support.apple.com/en-hk/guide/mac-help/mh35565/mac

You have to fill up the Apple ID password of her , and click on next and follow the upcoming instructions if the Apple ID is created with secondary authentication or 2FA .

If you want to sign her into iCloud, iTunes, and other services that require an Apple ID, it would be better to create a separate user account for her using System Preferences/Users & Groups. She can sign into that account and stay signed in. It will also keep your data separate.