You can make the USB, writing the image using dd or simply copying using cp command. Notice that writing the image destroys all the contents from an USB!

An example about making the boot-usb:

sudo blkid ### tells the drives and partitions

If the USB is /dev/sdb, writing to the USB goes

sudo cp bios-boot.img /dev/sdb

If using dd, the process goes

sudo dd if=bios-boot.img of=/dev/sdb