How do I add another phone from my acct to find me

Start here:

Keep track of personal items using Find My - Apple Support

Find people and share your location with Find My - Apple Support

All devices that you wish to track must be updated to at least the minimum system requirements (as documented within the link) - and be signed-in to iCloud with the same AppleID. Each device must also be enabled to use Find My (i.e., the Activation Lock has been enabled) in device settings:

Settings > [Your Name / AppleID] > Find My > Find My [Device] - set to ON

Follow this article to add friend to Find My, or another one of your devices that uses a different Apple ID.

Find people and share your location with Find My - Apple Support

You would need physical access to both devices to set this up.