You can't. Bones can only be dropped from skeletons, and they don't appear when the difficulty is set to peaceful. But if you want to get them easy, you can just change it to normal, and when you find a monster, you change it to peaceful again. The monsters will die and drop their items without any hassle.
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You may have your difficulty set to Peaceful. Monsters will not spawn in Peaceful mode.
If the difficulty isn't set to peaceful, mobs will spawn in creative mode.
Set the difficulty to peaceful so you don't see anything scary. in the game, Press escape, click options then change difficulty to peaceful.
You can set TNT off in Minecraft Beta by clicking it, or by triggering it with redstone.
Minecraft has a separate multiplayer server file to download for free. Just look for the links for the forums or look at Youtube to find out how to set it up.