This guide is designed to get you building OGRE from source with the default settings in the shortest possible time, showing you the barest minimum of CMake to do that, and minus any real discussion. Remember that there is a lot more to the hows and whys of this process, so it's a good idea to go back to the Getting Started With CMake page and read the whole thing when you have time.
We assume here that you've already downloaded / extracted the OGRE source code into a folder on your local machine. From here, go to the section for your platform.
Detailed instructions on building OGRE for iPhone can be found on this page Building From Source (for iPhone)