As a single Python script, txt2tags needs no installation at all.
The only file needed to use the program is the txt2tags script. The other files of the package are documentation, tools and sample files.
The fail-proof way to run txt2tags, is calling Python with it:
prompt$ python txt2tags
If you want to install txt2tags on the system as a stand alone program, just copy the txt2tags script to a system PATH directory and make sure the system knows how to run it.
chmod +x txt2tags) and copy it to a $PATH directory (
cp txt2tags /usr/local/bin)
After that, you can create an icon on your desktop for it, if you want to use the program's Graphical Interface.