The simplest way is to simply copy the files to a new destination, preferably a different hard drive. There are programs you can purchase that will perform backups automatically, just do a Google search.
I read your question again and I'm wondering. Are you talking about backing up images that are already on your computer? Or are you talking about copying images from your camera to the computer?
Thank you for this reply - am finding my way around Lightroom 5 - second
day in so help is most welcome! Probably the obvious when once known ...
it is a bit of hunt for the answers right now! Thanks again.