If you haven't done so already, create a new directory for installing the x-kernel. For the purpose of this report, we refer to this directory as /usr/xkernel. You may chose another name, however. cd to this directory and type
tar xf file
where file is the disk or tape file of the x-kernel distribution. This will create several subdirectories in /usr/xkernel. A description of the x-kernel directory hierarchy can be found in the README file at the top level of the x-kernel hierarchy.