Download the Ubuntu image for your device in your `Downloads` folder

Insert your SD card or USB flash drive

Identify its address by opening the “Disks” application and look for the “Device” line. If the line is in the /dev/mmcblk0p1 format, then your drive address is: /dev/mmcblk0. If it is in the /dev/sdb1 format, then the address is /dev/sdb

Unmount it by right-clicking its icon in the launcher bar, the eject icon in a file manager or the square icon in the “Disks” application