STEM is a standalone rich client platform (RCP). STEM requires at least Java Version 1.5. It also appears to run on Java 1.6. IBMers should obtain the IBM version of Java 1.5. Others can use either IBM's Java 1.5 or the Sun Java 1.5
You can get more information about installing STEM from here.
All downloads are provided under the terms and conditions of the Eclipse Foundation Software User Agreement unless otherwise specified.
Download the project and import it into STEM using File->Import...->Existing projects into workspace