This download contains IBM Installation Manager and a launchpad that is configured to install IBM Rational Publishing Engine. Extract the file into the same temporary directory, run the launchpad.bat file (Windows) or the launchpad.sh file (UNIX), and click the launchpad links.
If this is the first time you are looking to try RPE and you need a RPE trial license, please contact your sales representative and they will get you going in no time.