If you need a video, which may or may not exist, try searching for one, I suspect you won’t find anything.
In your case, I would suggest starting again with a live boot ISO, deleting any and all partitions you have on your target drive you want Kali installed on using GParted, formatting it to ext4, and then reinstalling Kali again, making sure you also install the bootloader to that same drive. That is IF you want a bare metal install on the external drive that will be bootable
If however, which is what I am suspecting you actually mean, you have simply ‘moved’ a VM file to a different drive, then instead of trying to boot it which will fail because it is no longer where the VM manager expects it to be, you don’t ‘move the boot’, you ‘import’ the VM image into the VM manager, pointing it to your new location when it asks where to import from…
And I am ‘listening’, but you are not being very clear, moving a VM doesn’t need a ‘boot sector’, that is all taken care of by the VM hypervisor, whilst a ‘bare metal’ install would require a bootloader, and is a different set up.
Bare metal or VM ?