Startup installing second new Passport

I’ve bought a second 4TB My Passport. I want to keep two copies of all my backup and switch from time to time. I removed the original one and plugged in a new 4TB Passport. But I can’t see how to see it and start it. Help!!

Also, should I copy everything? The first copy only copied some things. However, my internal hard disk, divided into C and D drives only total about 2.1TB. So I could backup everything. Should I?

What frequency is a good idea for backup?

Finally, should I leave both Passports plugged in to both back up simultaneously or will that slow the machine down?
Thanks all.

Hello,

WD Backup does an incremental backup. Every time you disconnect and reconnect a backup target or source device, the WD Backup software rescans the backup source device for new or changed files and resumes automatic backup protection according to the schedule.

Kindly refer to the following KBA article for instructions: Backup Your Files Using WD Backup for Windows