You can download additional JREs with the JRE download wizard. Click [JRE download wizard] to download the JREs you need. The drop down list will be updated after the download has finished.
If you wish to bundle a JRE that is not available from ej-technologies' download server or that has custom modifications (like an installation of the javax.comm API), please see the JRE bundle creation wizard on how to create your own JRE bundle.
install4j will automatically adjust the JRE search sequence of all generated launchers and include the bundled JRE as the first choice. The JRE will always be distributed in the directory jre right below the installation root directory.