It all depends on what device you have. In most cases, you will need a computer, internet connection, syncing cable and software(for computer). This software is dependant on the device. For example, a Samsung has something called Kies, Sony Ericsson has PCCompanion and so on. Also, whether or not the device has an available update to Jellybean is also a question. The older, and therfor less powerful, it is, the less likely this is. Just google and you can easily find a list of phones that are supposed to get the update. Just as easily, you can also find a set of device specific instructions for the procedure.