Copy the folder 

ews_backup

to a USB flash drive. This folder can contain one ore more backups. 

The backups are zipped files named by date.

Create a file called

ews_restore_latest.txt

on the USB flash drive.

Optional replace "latest" by the exact date of a backup in your ews_backup folder, in case you want to restore a different backup then latest one.

Insert the USB flash drive into the EWS and wait until the LED blinks again, then pull the stick.

To check if the restore was successfull open the USB flash drive and check the prefix of the ews_restore_latest.txt for "_success" or "_failed". 

For more details open this file with a TextEditor.