Almost every UNIX/Linux system contains Perl in default installation, so we may expect that you have already Perl installed on your box and you only need to install PerlTk toolkit and TrEd:
To install PerlTk toolkit, untar the Tk800.022.tar.gz archive to some temporary directory, e.g. with the following command:
$ gunzip -c Tk800.024.tar.gz | tar -x
and issue the following commands (see file INSTALL in the Tk800.024 directory for details):
Installation of TrEd on a UNIX box is same as on Linux. To install TrEd, the whole Tred folder from the CD (Tools/Tree_Editors/Tred/Tred) somewhere on your file-system, e.g. to your home directory or /opt directory.
You may also wish to install the tred executable to some directory in your PATH. In that case you have to provide a way for TrEd to find its library files. It can be achieved either by setting the TREDHOME variable to point to the location where you have made a copy of the Tred/Tredlib directory, or by copying the tred executable and the Tredlib directory into the directories bin and lib respectively, on the same level of directory structure. (The same holds for the btred executable.)
TrEd is ran by executing the tred executable or typing perl tred (in the later case full-path to tred should be specified). See details in Section 8.
If executing of the tred executable fails, try to change the first (#!/usr/bin/perl) line to point to your Perl executable. If you find TrEd halting immediately, complaining about Tk.pm module, check PerlTk installation path. You may need to setup PERLLIB variable to point to the site_perl directory on your system to which the Tk.pm module was installed.