How to use “usbboot” command

When my machine is booting up the very first screen it the one with the Libre logo (don’t remember what it’s actually called at the moment) I want to boot from USB but when I type usbboot it says no usb device specified, which makes sense, but I don’t know how to specify which port/device it’s gonna boot. How do I use this command?

You don’t need the usbboot command. You can use the libretech-flash-tool to flash the bootloader onto a clean formatted MicroSD card, then flash any image onto USB, and it will boot.