Select the item you want enchanted. Then, find an anvil or go to the enchanter. Save and quit the game. Then, load the game and enchant the item. If the enchantment is not to your liking, do not save and quit. Instead, press [Ctrl] + [Alt] + [Delete] and close the game in the Windows Task Manager. This will exit the game without saving. Start the game again and repeat those steps until you get the desired effect.