How do you add a device

You must fully sign-out from the AppleID on the device - before you’ll be able to sign-in with a different AppleID. When you sign-in to iCloud with the new AppleID, the device will be associated with your AppleID account.

iPad 7 generation and iwatch 5 series I have two different Apple ID so I wanted to add those to my iPhone XS ID, I all ready removed the from LisaLawrenceShack’s Apple ID account and ready to deactivate,

I am aware of that I am trying to connect now by removing them from the old Apple ID to the new one. But I can’t find where to add a device I can pull it up by entering the serial number but can’t figure how to emerge with latest Apple ID

What type of device are you attempting to add - and to what are you attempting to connect?

Writing an effective Apple Support Commun… - Apple Community

All your devices, must use the same AppleID.

They are all apple products