(Note: This assumes you have already set your HEADAS environment variables with the
headas-init script, as you would if you were running XSPEC.)
To make sure your XSPEC installation is up to date with ALL listed patches:
1.    If you don't already have the patch installer
tcl script (v4.9), download and place it in the XSPEC src directory. This directory
should be at heasoft-[ver]/Xspec/src from the source code distribution.
2.    Download the latest patchfile into
the same directory. There is no need to unzip/untar the patchfile
since the installer will do that.
3.    At the command line, launch the script by typing
and that's all.
The script should detect which patches you've installed previously, copy
the new code files to the necessary directories, determine whether complete or only partial
rebuilds are necessary, and finally perform the rebuilds. Numbers listed in red indicate that the patch modifies the interface
to one or more of XSPEC's libraries. These patches will generally cause longer rebuilds. If you
have a local model library, it is recommended (though not always necessary) that you rebuild it
with initpackage after applying red patches.