depending on how much free space you have on your drive and the size of your home folder, the easiest way would just be to
- boot into some live image with gparted (basically any live image)
- use gparted to resize your root and add a new partition for /home
- copy the whole /home folder contents over to the new partition
- if you want your existing install to work: edit your fstab to mount the new partition as /home. the arch wiki should have good instructions for this, doesn't matter if you aren't using arch
