Read the README file.
For a quick start:

Installation
============
gunzip and untar FSViewer.app-0.1.0.tar.gz
[prompt]$> tar zxvf FSViewer.app-0.1.0.tar.gz 
or
[prompt]$> gunzip FSViewer.app-0.1.0.tar.gz
[prompt]$> tar -xvf FSViewer.app-0.1.0.tar
then
[prompt]$> cd FSViewer.app-0.1.0.
[prompt]$> ./configure
[prompt]$> make
if the make goes ok su to root and
[prompt]$> make install
or 
[prompt]$> make install-strip
return to normal user mode and
[prompt]$> cp ./FSViewer ~/GNUstep/Defaults/.

The icons are copied to /usr/local/share/FSViewer.app/icons.
The executable fsviewer is installed in /usr/local/bin.

If you can't su to root, then use --prefix=/a/dir/you/can/write/to in the 
args to ./configure. For example:

[prompt]$> ./configure --prefix=/home/users/clernong/local
[prompt]$> make
[prompt]$> make install
or 
[prompt]$> make install-strip
[prompt]$> cp ./FSViewer ~/GNUstep/Defaults/.

fsviewer is now in /home/users/clernong/local/bin
The icons are now in /home/users/clernong/local/share/FSViewer.app/icons.

It may be useful if the directory the icon directory is added to the Window
Maker Icon paths. WPrefs.app can be used todo this.

