Make a copy of a creative defualt map in minecraft?

1: Go to your Minecraft Directory. Type "%appdata%" without the quote marks into the windows search bar (I assume you're using Windows 7)

2: Open the folder named "Roaming"(without the quote marks once again), and then the folder named ".Minecraft". In there, you should find a folder marked saves, open that.

3: Find the world you want to copy. The world names will actually be what they are ingame. Copy that worlds file, then paste it to the saves folder. It'll automatically be called "<The name of your world> - Copy"

4: Load up minecraft and enjoy your copied world. You can also send that world to others by sending the save file to them.

Is this the PC version of Minecraft? I'm assuming you're talking about making a mod of some sort that you were expecting to see but didn't? Before making any modification to any game, I would suggest making a backup of the non-modded version of it somewhere on your computer. Then make any modifications on the copy of the game you intend to change. When the changes are completed, save it and launch the newly modded version of the game to see if it works. If you don't see your change, I would double check the files that you're making changes to are the files that will effect the changes you're hoping to see. Since I've never modded Minecraft on a PC before, I can only speculate, perhaps someone with more modding experience with Minecraft would be able to help you out. Perhaps check the Minecraft modding forums?

1. On Finder, on the toolbar go to Go

2. Hold down alt and select library which only appears when holding down alt

3. Go to Application Support - Minecraft - saves and copy the save and rename it something different.

You can also load up minecraft, go to recourse pack and select open folder, it will bring you to the recourse pack folder, press the back button and you will be in your minecraft folder.