If you are using macOS, you have two options. Either you can use a graphical interface tool, like Etcher, or you can use the built-in tools. For non-expert users, we strongly recommend that you use a graphical interface tool.
In the video below, you can follow the process from start to finish.
If you prefer to use the command-line tools, first identify the device using
df -h. With that done, simply replace rdiskX with this device.
diskutil unmount /dev/diskXsY
unzip -p /path/to/screenly_image.zip | sudo dd bs=1m of=/dev/rdiskX