using WD my passport for mac

I'd suggest setting it up with Time Machine. For 12.4 you would need to format it in APFS and then select it in Time Machine.

Back up your Mac with Time Machine - Apple Support

As an aside, I personally I don't like the WD My Passport. I have one myself. My issue is that this series has always used a proprietary interface that connects directly to USB and not a SATA drive with a SATA to USB interface. With the latter, if something goes wrong with the interface or connector, the drive can be removed and used in an enclosure. I've heard Seagate external drives typically use a SATA drive.

DonGato2015 Said:

"using WD my passport for Mac: have not backed up my late 2013 MacBook pro 13 retina for 5 years using Catalina 15.7 os looking for directions on how to correctly do this"

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Backing Up Catalina with Time Machine:

Research the model of this drive to make sure it is compatible with your Mac model and macOS version.

If Compatible:

Format the Drive in Recovery Mode:

Backup what need be from this drive, then proceed with a format. Hold down: [command + R] > Select: Disk Utilities > Format: the drive to APFS. In doing so, it will be erased, and will be made for Catalina Time Machine Backups. The, create your first backup.

Hi,

See: Back up your Mac with Time Machine - Apple Support

You could also use SuperDuper! or Carbon Copy Cloner to create a bootable clone.