The distribution contains several subdirectories which contain TEX style files, METAFONT files, and various kinds of font information. These should all be installed into the appropriate places on your computer system. Ask your local system administrator or TEX maintainer if you are not able to do this yourself.
Once things have been installed properly, you will be able to use the evaltrace style by specifying the ``evaltrace'' option in the documentstyle command. For example, the documentstyle command for this document goes as follows:
\documentstyle[12pt,fullpage,evaltrace,code]{article}
The ``code'' option isn't really a part of the evaltrace style, but is often useful in documents that use evaltrace. Thanks should go to Jon Rees at MIT for providing us with the code style.