To use LaTeX2HTML simply type latex2html <file>.tex. This will create a new directory called file which will contain the generated HTML files, some log files and possibly some images. To view the result use an HTML viewer such as NCSA Mosaic on the main HTML file which is file/file.html. This file will contain navigation links to the other parts of the generated document.
It is possible to customize the output from LaTeX2HTML using a number of command line options with which you can specify how to break up the document, where to put the generated files, what the title is, what the signature at the end of each page is, what to put in the navigation panel, what kind of extra information to include about the document, whether to retain the original LaTeX section numbering scheme, etc.
Also, the LaTeX2HTML script includes a short manual which can be viewed by saying
%nroff -man latex2html .