How to add persistence to entire Kali filesystem?

So I've set up a live USB with Kali for pentesting, and I'm now trying to get persistence working on it. So far, the USB has been partitioned and an ext2 filesystem installed.

When I open Kali, there is an unusual folder on the desktop with the icon of a hard drive disk whose name is MyPersistence, the name I chose for the persistence partition. The path of this folder is /media/root/MyPersistence. Anything I save in this directory gets persisted correctly.

However, nothing outside the directory gets persisted at all.

At the Kali boot menu, when presented with options, I hit tab and it brings up a small console pre-filled with this command:

.linux /live/vmlinuz noprompt cdrom-detect/try-usb=true boot=live username=root hostname=kali initrd=/live/initrd.img

According to instructions I've followed, I'm supposed to add persistence as a parameter to this at the end, and run it. But this produces no apparent change, nothing is different. What is that parameter? Is it supposed to be the name of the partition, MyPersistence in my case? What is .linux and where can I find more information about the parameters it takes?

Additionally, there was this in the instructions:

mkdir -p /mnt/my_usbmount /dev/sdc2 /mnt/my_usbecho "/ union"> /mnt/my_usb/persistence.confumount /dev/sdc2 && reboot

But it also has no effect.