Messages on Macbook from phone number
How do I set up where I can receive messages on my MacBook Air from my phone number connected to my IPhone if they are under different iCloud emails?
MacBook Air 13″, macOS 11.6
Different iCloud emails implies you want to use a different Apple ID exclusively for messages from that iPhone. Is that correct? You would need to "Sign Out" of your existing iMessage Account on the Mac, and "Sign In" to the other Apple ID.
Sign in with your Apple ID - Apple Support
Change iMessage preferences in Messages on Mac - Apple Support
I do not believe it is possible to enable two separate Apple IDs for simultaneous use with the Messages app, but I could be wrong about that. I just don't know of a way to do it.