Hi there, I have started using Ventoy recently, but I have a question, where do I install the OS that I use in Ventoy?

do I install it to the hard drive, or just live boot, I would love any help.
What exactly do you mean?
As per the guides, the Ventoy software will turn your USB into a bootable key, and after you will transfer ISO's of Operating Systems to the USB drive, then boot up ventoy on a machine, and select the ISO you want to boot into.
See:
https://ventoy.net/en/doc_start.html