How do I use 2 HDD's for old PC running Debian?

[MC.Morrado]

I just ordered a hard drive caddy to fit a pair of 2.5-inch SATA HDD's for a Linux PC that I mainly plan on doing command line stuff on. How do I install the operating system on one hard drive but store stuff like documents, music, pictures, and stuff on the second hard drive? The first HDD will have the operating system, installed programs, productivity software, and other stuff actually installed on the operating system.

 

Do I do all of that after installing Debian and/or Debian-based distro onto the first hard drive? Operating system: Q4OS. Any input is much appreciated!

[Electronics Wizardy]

Since the drive is for non OS stuff, I'd set it up after the main install. Partition and format the drive as you see fit, then add it to fstab to mount automatically.