I want to sync Contacts from my Mac Monterey to my partners iPhone 7.

I want to sync Contacts from my Mac (which we share) to my partners iPhone.

It synced just fine with mine - which scares my Apple ID.

I have read some threads, but don't understand how I can sign in with two different Apple IDs.

eg which machines have to have both Apple IDs?

Can I actually add a second one on an iPhone 7?

If this is the only way, please explain in simple steps, with no missing steps

eg It was suggested to go to Mac Settings - which isn't anywhere I can find. I have system preferences.

I have also tried to achieve this by using Mac Finder and selecting the her iPhone.

It says that it is syncing contacts - but it actually isn't doing anything different.

Or perhaps it is syncing her contacts in iCloud back to her phone.

So I scroll down to Advanced: and check the box to Replace Contacts.

Then I press sync.

It rolls through step 2-4 and unchecks the box - but nothing has happened.

Same old groups and same old contacts.

Apologies if this is obvious to you - I have tried many many times to achieve a simple task.

Help please - much appreciated. J