There are 3 steps:

1. Install HTML::Latex - 'cd HTML/Latex' and then read it's INSTALL. 

2. Copy html2latex to anywhere you like (/usr/bin is a good place for
a UNIX machine).

3. Copy html2latex.1 to /usr/man/man1/ (for unix machines only).

So, here is an example of what you might type (Assuming everything goes ok):

cd HTML/Latex
perl Makefile.PL
make install
cd ../..
cp html2latex /usr/bin
chmod +rx /usr/bin/html2latex
cp html2latex.1.bz2 /usr/man 
chmod +r /usr/man/html2latex.1.bz2