Nanowire is a simulation tool for silicon nanowire FET's in the nanometer regime (diameter <= 5 nm) where quantum effects are important and (channel length <= 10 nm ) where transport is mostly ballistic in nature. The first-time user guide shows how the tool works and offers examples. After going through this guide, one should be able to understand the basic workings of a nanowire and be able to play with the code using different parameter sets. It is assumed that the intended user has basic knowledge of the Non-Equilibrium Greens Function approach (NEGF). If needed, the 659 series of lectures on Quantum Transport would be a good source to consult to understand NEGF.