How can I transfer iJoomer app to XCode iPhone simulator? I downloaded iJoomer in iTunes, and I would like to transfer it into XCode's iPhone Simulator so I can run the app there. 

Is it possible to transfer an app from iTunes to the iPhone simulator? If so, how can I do this?
The short answer is no.

The reasons are numerous, but the first is that anything compiled to run on a device can not be run in the simulator because the processor architecture is different. The simulator is simulating a device, not emulating a device. Apps run in the simulator are intel x86 binaries, while apps that run on a device are compiled for some version of the ARM processor.