To backup your RouterBOARD configuration log on via the Winbox and select the Files menu item:
Click the Backup button and then simply drag the file from the GUI onto your desktop. To restore your configuration simply highlight it and click the restore button. You will be asked to confirm and then reboot your device:
If the file you want to restore is not one the device then simply drag it into the files list and it will be copied up to the device.