AIR includes graphical user interfaces for two of the most frequently used programs (alignment and reslice). These interfaces are written in Tcl/Tk.
You would need to download the AIR package and follow the instructions here
http://bishopw.loni.ucla.edu/AIR5/tcltk.html to set up the environment for the AIR GUI.
Alternatively, you could run the AIR programs via LONI Pipeline, which can be downloaded from
http://pipeline.loni.ucla.edu/. A corresponding user guide can be found here:
http://pipeline.loni.ucla.edu/support/user-guide/. Once you have registered for a Pipeline user account, downloaded and installed the software, you can connect to the LONI servers and use the set of packages in the Pipeline library. Among the tools integrated into Pipeline modules are all of the AIR command line applications.