Backing up on macbookpro and macbook air on same my passport

Please can you advise how I can back up 2 different macbooks on the same" my passport for mac" 1tb. Currently backing up first laptop but want to understand how to segregate for 2nd macbook if possible. Many thanks

Welcome to the Community.

How are you performing the backups? Do you WD SmartWare or do you use Apple Time Machine?

Hi - Apple time machine

If so, you only need to safely eject your unit and start Time Machine in the next computer after ensuring it uses a different name.

Thank you solution found