Insert Minecraft saved world in Minecraft Mac OS X?

I got the latest version of Minecraft, and then I was told to make a backup, but how do I get there?

I know how to get into the Minecraft folder, I just don't know what I have to do to possibly overwrite the world.

I ask for sensible answers and step-by-step instructions for a technology dummy like me.

First of all, what kind of mac you have is important

you go to your home screen there's go to the top of the bar and hold old or option depending on how old your mac is then you click on library what opens then on application support then go to minecraft there's then saves and there are your worlds inside.